takebacks and bad sportsmanship

Confirm move would be a nice option. But then people would complain about losing on time because they forgot to turn off confirm move when they were approaching time trouble.

Confirm move + being able to set it to automatically disable with X time remaining would be great.

Mouse slips are annoying.  But I have seen even GMs do them, and their opponents usual response is to laugh and point, a bit like any other mess-up in a game.

I kind of agree with you in principle, but I think it would be abused more than it would help.  It's very easy to claim a bad move was a mouse slip (even though sometimes it's true).

And really, it barely matters in the long run.  You will lose this way once in a while, and you will win this way once in a while.  Evens out.

On another site, my opponent played the unsound sacrifice ...Rxh3 and claimed mouse slip. I let him take back the move, and he played ...Na6. That was a spectacular mouse slip!

Well that just means people prefer to live with mouse slips then. An “Are you sure?” dialogue box would be an easy fix too.