"so my fat ass got to whining"

Player picks race with a culture that has strong gender roles that say only men learn to read, even if you're a highborn.
> Oh but I am special so can't I just <makes up something incompatible with setting>.
And then when the DM says no, they blame the DM.

People who can roleplay only 1 thing and can't adapt it to the setting but rather demand the setting adapts to them.

So the other 10% shave it after it all grew back?
Nope! Cancer!

Basically weed infused candy

Trooper

This is so sad.
100 years ago we would just let these people play outside, usually by the river, until one day they just didn't come home anymore and we'd tell ourselves that they just went to explore the big city.

Typical sugar withdrawal.

Okay I know this is hypothetical but I'mma try to break this one down anyway.
It sounds like entities like demons are already in the game, so there is likely a model for it.
Summoning also sounds like it is in the game, or at the very least spawning. There is no condition for summoning so no items or abilities need to be made, the player can simply do this thing.
Lava explosions either already exist in the game or the game is written using some engine that likely has good support for this. After all, explosions are a common thing to want in games. The difference between lava and rubble is likely just texture and maybe a bit of physics tweaking.
Making a creature rise from the ground is easy too.
There is hardly anything in the game that needs to be changed for this feature to be added. In other words, this feature is simply adding stuff, not changing existing stuff.

Giving the player a scarf on the other hand means that you either have to edit the character model or add an object that has to move with the player. A lot needs to be edited about the player for the scarf to properly move with the player. If the game is first person then the scarf must also not obstruct any vision (but why even have a scarf if it is first person anyway). If the scarf is loose it must also have physics, which will constantly collide with the player which might be a performance issue, look stupid, and/or affect other player collisions as well. The latter issue means you'd have to test for clipping in so many new places.