On a slightly different note: In my opinion, Unwinnable by Mistake was split in the worst possible way, with only the "Other Video Games" section moved off. Apparently, an "other video game" is one that doesn't belong to any of a few arbitrary categories that got sorted out earlier.
I was mulling this topic over last night, but perhaps some clarification is needed on Unwinnable by Design's part. Versus Unwinnable by Mistake, it all comes down to the game's core design theory. UBD isn't UBM But More So, it isn't about whether the Unwinnable situation was intended by the QA team.
UBD is where the responsibility for avoiding Unwinnable scenarios rests on the player (whereas in modern games the designers take it on themselves to always leave the player a way to continue onwards). Discovering that one of your saves has become unwinnable, then going back to a previous save file and picking up that Chekhov's Gun you ignored the first time is just another puzzle, a meta-puzzle, that lasts the entire game long.
I think attempting to divide UBM between "obscure combinations of actions" and "simple actions that got past QA" is ... not that much of a difference. Yes, they originate differently, but I'm not sure the end result is all that noticeable.
An Ear Worm is like a Rickroll: It is never going to give you up.

Yeah, and I deliberately patterned it off some examples (now moved to the subpage), particularly the following pokemon one:
Similar:
- There are many situations where you can trap yourself or make a puzzle unbeatable; the developers have figured out most of them and made Glados deliver another cube or open the door if you manage to do so. There are, however, several ways to trap yourself that they haven't thought of, such as piling cameras under the weighted companion cube to support it while it's partway on the button, going through the door where the button to open the incinerator is, and then shoot a portal to make the camera fall through and the cube come off the button, so the door closes and you're trapped.
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BTW, I'm a chick.