Well now that we're on the subject and in the proper thread for it, Nuzlocke isn't a good playstyle. The games aren't designed well around them, and I don't know why people enjoy so much throwing 12 hours of game time down the sink so readily.
I think Nuzlockes present a more extreme version of a problem I encounter when playing pretty much any RPG: the more knowledge you have, the less exciting it is to play through the game. The feeling of discovery and improvisation in a world of boundless possibility is one of the main draws of the genre, so you get diminishing returns each time you replay it. It's worse for the Pokemon games because there's no execution element to the combat (not that I think there should be), so any battle you're familiar with from past experience will mostly be decided in advance by your team composition and intended strategy, just with the possibility of being helped or hindered by hax.
Nuzlockes encourage safe, careful play to protect your mons from 'death'. Provided you don't add rules to limit item use and/or overlevelling, there's no reason why you should lose any battle that you can grind for beforehand. If you
do set reasonable limits to make it fairer, then you can definitely lose, but only as a result of bad luck (available encounters, hax) or a gap in your knowledge.
Some professional Nuzlockers optimise their play to such an insane degree that they're literally going into each major battle with a full list of how each turn could play out and how they'd respond. Every attack is calced and they have perfect knowledge of what the AI can choose to do in any situation. It's common to hear 'as long as X doesn't happen, we win' which means the entire battle is just waiting to see if they get crit at an inopportune moment or whatever. It works ok as entertainment because there's a sense of a community being bonded by the tension, but on your own I find it's mostly just frustrating or boring.
I much prefer challenge runs with pre-planned teams (which I'm sure have the same issues for other people), because I think it's more satisfying to have all your team limitations defined from the start so you're free to strategise as much as you like within that predefined space. Monotypes and other themed runs (genderless, specific animal types, stat trainer team, etc) have a fun little narrative element that isn't as serious as the forced attachment/tragedy aspect you often see in Nuzlockes.
Wow this thread blew up while I was away
Anyway here's my probably-awful game mechanic take: I've never really understood why Trick Room doesn't work on priority instead of on Speed stats. It's really weird to me that the move makes slower Pokemon move first but you can still use Quick Attack et al to get around that, sort of defeats the purpose.
I guess game balance is the reason because otherwise Iron Ball Rampardos would probably murder everyone and everything but idk.
I think it's more about preserving the mechanics of moves with negative priority, which are often either balanced around their priority bracket (phazing moves etc.) or require going second to work (e.g. Mirror Coat/Counter).