Suggestion: Have an option where opponents cannot give you extra time

But wouldn't this in the backend just be adding a new column to the preferences schema? Why would that make a migration off of MongoDB harder?

The data representation of a preference is the easy part.

Seamless integration in the supported browsers/browser versions and mobile applications/application versions (both with ability to change preferences mid-game, and ability to add time) across all game types (simul, arena, against the machine, against BOT accounts) every time any piece of any of that code or the code that interacts with upgrades is the hard part.

I don't see why this hasn't been added already since the remove takeback requests exists. I'd use it, I don't like when people give me more time -.-

It makes any win feel meaningless and losses feel even worse.

"I don't like when people give me more time"
I am the same, I don't want to get carried away, but I think it is outrageous that people can give me extra time without my permission

Sometimes, my opponent begins the game with adding a lot of time by clicking indefinitely on the plus button. It's so stupid and I tell him. That's just annoying. Most of the time, it comes from a child having fun with that. The result is that I often block him.
There would be too many reasons to block players :
- leaving the game when they lose
- letting the time run when they lose
- "offering " draw when they lose
- insulting me when they lose
- adding much time as there is enough time (I always play with much time, because we need time to avoid mistakes and make nice combinations).

I thought chess was a game for civilized people, but this is not always the case !

"Seamless integration in the supported browsers/browser versions and mobile applications/application versions (both with ability to change preferences mid-game, and ability to add time) across all game types (simul, arena, against the machine, against BOT accounts) every time any piece of any of that code or the code that interacts with upgrades is the hard part."

seems like this feature is trivial to implement IMO, I think I'll reach out to the open source channel & see if I can help implement it!

Seems there is *already* code in the UI for hiding & showing this button (a function called `moretimeable` which currently only checks the player's remaining time to hide/show the button) - so that settles the problem of UI implementation & maintenance! All we would need is a DB option & to decide where in the UI the configuration should go - maybe a game setting where neither player can add time? (I know of Leagues that would appreciate this since it would conform to USCF / FIDE rules) - then add this config check to the moretimeable function

It appears "moretimeable" has two definitions and three references, one file of which (RoundDuct.scala) was modified this month:
github.com/ornicar/lila/search?q=moretimeable
... and all of which pertain to the Game object rather than to the Player objects.

Also even if we hid/disabled it in the UI, opponents could un-hide/un-disable it (or use the mobile application? I don't know its capability) so server-side validation might be a good idea.

FYI, this month our lead developer is refactoring code to improve scalability and performance:
github.com/ornicar/lila/commits/master

If you do succeed in merging a new setting, I'll give up on trying to develop increment for correspondence - the clock is already quite complex and I don't want to risk breaking other developers' changes:
github.com/ornicar/lila/issues/4462

Yes, I agree. This option is redundant and frankly, I've never seen anyone use it with good intentions in an even position anyway. It is only used to mock the opponent who is lost anyway. "Here, take extra 15 seconds, and more and more, you're dead anyway, I'm enjoying humiliating you"
It only adds to the irritation when you are already pissed off that you messed up the game.