Mainly, when a player disconnects/reconnects and when a player is killed (as well as by who). This would explain the abundance of seemingly random swearing that I see often in chatlogs, as well as how long someone disconnected (to judge whether it was intentional).

It's hard to judge disconnects as intentional or unintentional unless the players themselves admit it in the chat log. If they don't admit to anything, and there're no recurring infractions over a short period of time, then you have no evidence, and judging "punish" would be baseless and abusive.

But you can see if they left after dying (aka ragequit) or some other instances, instead of just basing your judgement on reporter comments and what you infer from the chatlog.

Seeing if they actually disconnected would at least help with false reporting. Right now it's very easy to claim someone left during the last minutes of the game.

well seeing someone DC after 2 deaths and never return would certainly indicate something to me.