Thread necromancy! I want in on this.
1. DMPC party informs us that we're going to take a quest, or else. Are they forcing us? No, other than tying our characters up and gagging them when they protest. But they're really nice DMPCs, we should love them and do as they say. And they can kick our asses, so we'd better do it. That's one kind of character hook, I guess...
2. DM rules that something our characters tried and failed at (bribing a supposedly friendly NPC with pie, which it's been established that this NPC will do anything for said pie - and the NPC is the only one that can help us out of our prison, but currently "doesn't feel like it") - with no rolls - is automatically successful when their DMPC does it, immediately after our failure ("Do you want pie, NPC?" "Pie, yay!" *fetches the key to our cells for the DMPC*).
3. We come upon a canyon full of evil fire giants who plan to destroy us and the outside world. For some reason their canyon is dry, despite being a few yards from a huge underground lake. My character wants to use the Dig spell to dig a furrow that will lead the lake into the canyon, flooding it. No "it can't flood it fast enough." No "that's not a good idea, for these reasons." No "the stone floor is too hard," or anything of that nature. Just, "you can't do that." Apparently the spell can't even be cast. So we all are forced into melee with the fire giants, during which we're captured and (of course) our bacon is saved by the DMPC party.
4. The DM informs us that we're actually NPCs in a game she's playing with some other people, who are the DMPCs. That's why we couldn't be allowed to have any effect on the campaign, NPCs or surroundings. She believes this information should make us proud to have been allowed to play with these characters.
Yeah, I had to ragequit after that.
1. His main favorite move was "you lose control of your character, he does terrible things. Now you're back in control." Used sparingly, this might not have been annoying. As a regular event, it left me wondering why, when he had the ENTIRE REST OF THE WORLD to play, he felt compelled to control my character, too. My "favorite" example of this was when he said that due to being infected somehow with some kind of seed of evil/demonic possession, my character turned into a horrible demon and raped his girlfriend. And enjoyed it. That last detail is pretty much the final straw.
2. His second favorite move was "it was all a dream." Again, used sparingly, it wouldn't have been so frustrating. Used so often that basically half of everything my character did was annulled, though, it was... aggravating. (Note: the event above was not one of those times. Not that it would have been okay if it was.)
3. I actually really liked his NPCs... back when that's what they were. They were living, thinking beings reacting to their world in an interesting way, with interesting personalities. Then they became DMPCs. The difference, to me, is that NPCs are there to make the game interesting for the player. DMPCs are there to show off how cool the DM thinks he is, usually via nerfing, belittling, and/or beating up the PC(s). Towards the end, it seemed like he'd have been happier writing a book about his DMPCs - and, it seemed, casting my PC as a rather unpleasant sidekick.
4. Finally, this DM loooved to make short statements, then make you fish for more information or try to play off the complete lack of information he'd given you (we played online). He would post a short sentence someone had said, without mentioning who. He would have his characters mock plans I made based on what he had told me, because the truth was something else - which my character should have known, but didn't. Because... actually, I have no idea why. I think he was just a prick. This got really old, really fast, but he didn't seem to know what I was talking about when I asked him, politely, to tell me what my character would know about any given situation. From the environment, to which of the NPCs he knew well was talking to him, to basic knowledge about the world that anyone should know, to specific knowledge that only my character COULD know, and absolutely should... either getting more info was like pulling out teeth, or I got smacked down in-game for acting on incomplete information.
5. OK, bonus round: Towards the end, my character couldn't do anything right, despite being (supposedly) high-level. He could just about handle what an 8th level fighter could (he was a gish-type character); everything else either failed, was made irrelevant, or was impossible for whatever reason. I couldn't affect the world or the story at all, which I'd be less annoyed with if it were some railroad module game. But it was a freeform game. Turned me off them, for sure. At least if you're following a ruleset, the DM has to make an effort/explanation to nerf you, rather than waving his hand and doing it by fiat.
I actually really wanted to give this guy a chance to redeem himself, because his early games were a lot of fun, and he was one of my oldest friends (we're talking 1st grade)... but finally he just didn't show up at the agreed time for a meeting. And then the next, and the next... I even wrote him a physical letter asking him what was up, and he never answered. That was 6 years ago. I know he's okay, because he's on social media. He's apparently just more of a jackhole than I thought.
I guess he wouldn't have changed, anyway. He was, self-declared, proud that he'd never played in a game. Not one, in any system OR freeform. I'm not sure how ignorance of half the table experience is a virtue, but to him it is, I guess. It sure explains his DM faults (at least, they're faults in my eyes). I'll always wonder how that game's story would have ended, though. It was pretty entertaining, despite everything.
Whew, that got long. Thanks for letting me rant, it's cathartic.
Edit: Threw things under spoilers to not eat the whole page.