Andy E. Nystrom wrote:

When a story gets too preachy and spells out the moral of the story instead of letting the fiction act as allegory. Example: In John Q, John holds hospital workers hostage, resulting in the workers discussing how correct he is about the flaws in the US medical system. His points might be valid, but even if your political views are the same as the hostage taker, your focus is going to be to escape with your life, not the merits of the hostage taker's point of view. There was also an episode of Supergirl involving violence towards transgender people that could have been a strong episode, except the hammering home of the points felt unnatural, Had the characters talked like normal humans and the writers let the audience reach the obvious conclusion they were aiming for, the episode would have been stronger than just telling the viewers what to think.

Try Orphan 55 in a recent season of Doctor Who, where at the end of an episode about environmental collapse (e.g. global warming, etc.) the companions ask the Doctor if Earth is going to fall victim to same and the Doctor's response is done as if she is addressing the audience rather than her friends as she basically delivers a "no, but we all have to do our part fighting climate change" lecture, with less subtlety than an old sitcom "very special episode" delivering its final "moral of the story" moment. It's cringe-inducing.

I think the late writer Terrance Dicks summed it up really well way back in the early 1970s, when he was writing for Doctor Who (and the word "political" in the quote below can be swapped out for "moral" or indeed dropped entirely and the point still holds). He was more than happy to include moral and political views in his stories, but first and foremost he felt the story had to be good. That had to be the focus, not the message. "If you're concentrating on putting over a political message rather than on doing a really good show I think there is a danger - you know maybe you can do both, but it would be hellish difficult - and I think there's maybe a danger the show wouldn't be as good as it could or should be because you're not looking at the right aims."

Andy E. Nystrom wrote:

Another pet peeve: mostly found in 1970s-1990s comics but also found in in TV shows with a lot of continuity: forced recap dialogue. You definitely want to bring viewers/readers up to speed, but let the "Previously On" or Recap Page (which admittedly didn't exist in a lot of comics for along time) do most of the heavy lifting and only do an in-story recap if you can make it feel organic.
 

Yep. I mean, an easy out for the writer, albeit not one you could use every issue, would be for the characters to meet up with others who then need to be given brought up to speed with what's happened. 

Another peeve of mine: Characters who know they are in a crisis situation, but then when asked/told to do something by someone whose judgement they have no reason to doubt, decide to demand reasons why they should do as asked before they comply. To be clear - I am not meaning situations where someone is asked something outrageous (e.g. "shoot that guy who looks like your friend"), or by someone who they have reason to distrust or think has poor judgement, or doesn't know that something bad is underway and so gets caught off guard. I'm meaning the idiots who (for example) know there are sprint-zombies around and then when someone comes running like a madman in their direction shouting "run for your lives" stands like a prat going "why?" Gee, take a guess genius! 

The example that crystallized this whole trope for me was in the Jurassic Park novel, where

a group of characters are in the main building and need to reactivate the power. As in the movie, the switch is in another building and there are velociraptors outside. The main building is surrounded by a high fence which is normally electrified, but even without electricity is too high and too sturdy for the velociraptors to get through or over, but someone needs to go out a gate to get to the other building. So Ellie Sattler volunteers to go outside the building, but still within the safe fenced area, and basically dance and shout to draw the raptors' attention - she'll stand on the opposite side of the building from where the other volunteer needs to exit to get to the power switch, and once most or all the raptors are drawn to the part of the fence she is at (but on the opposite side), the other volunteer can make a run for the switch. At first this plan seems to be working, but then someone still inside the building recalls that there is a tree that overhangs the fence - while the electricity remains on, that's not a problem, as the branch that goes over makes contact with the fence, so anyone trying to get over the fence using it would be electrocuted. But now... Realizing that they can't be sure if raptors might be able to climb a tree, one of the people inside the building opens the door and shouts urgently for Ellie to get back inside NOW!!! And here's where the peeve I mentioned kicks in. Knowing there are dangerous dinosaurs on the loose, having no reason to distrust the judgement of the guy shouting at her, and with common sense suggesting others might be privy to vital info you lack, Ellie nevertheless fails to do as asked and instead shouts back asking him "Why? I'm fine." He shouts at her again to just do it because she is in danger and to get inside, and AGAIN she demands to know why she should do so before she complies. As he starts to shout the third time to explain, he is killed by a velociraptor that had indeed circumvented the perimeter fence using the overhanging tree. Ellie, annoyingly, manages to survive, but

as is so often the case in these instances, her stupidity and unwillingness to follow a sensible instruction because she insisted on having reasons explained to her at the worst possible time got someone else killed.

Andy E. Nystrom wrote:

Another one: Shows "on the bubble" ending a season (or series in the British sense) on a cliffhanger. If the show doesn't get renewed the viewer usually never learns what happens. Some next season set-up okay, but nothing too game changing. Examples: Agent Carter season 2 (which resolved the season plot but concluded with the start of a major new mystery; rather surprising since it barely got renewed after season 1), Legends of Tomorrow season 7, The Fugitive second series in the US sense, season 1.

British SF series Blake's 7 did this, but in their case I think the creators pretty well knew it wasn't going to get renewed, so the ending served either as a cliffhanger if the renewal did come, or a deliberately dark and depressing ending, in keeping with the overall tone of their universe, if not renewed. Having spent four years fighting the oppression of a galactic dictatorship (the Federation), and with former main cast characters either KIA or MIA during that time, including having the former, always-altruistic lead (Blake) going MIA and presumed dead to be replaced by his much more ruthless and cynical second-in-command (Avon), Avon finally thinks he has located Blake; with their base compromised the heroes flee just before it is destroyed, and head to retrieve Blake, but their ship is shot down on the planet Blake is believed to be on, destroying the sentient computer who was counted as one of the team. The rest of the team find Blake, but he appears to have lost his way and become morally compromised, so a betrayed-feeling Avon guns him down just seconds before Federation troops arrive in force. Each and every member of the team is shown being gunned down one by one, until only Avon survives, still standing in shock over the corpse of the friend he just murdered. Avon is surrounded by Federation troopers with their guns pointed at him virtually point blank, and he seems to only now become aware of them. Smiling cynically, he raises his own gun and the screen goes black as the credits start to roll, accompanied by the sound of gunshots.