
1. The server is at fault, so if the reason for a ban is "excessive lagging", then a warning should have been given.
2. A lag cap can never be implemented due to an unstable server, so the only thing that can happen is to give players warnings. Then again, you will have many players that will start complaining about getting warned.
Idk why people are complaining. You guys just need to learn how to beat her. She shouldn't be banned for excessive lagging, if she was not given a warning. Then again, staff usually ban people immediately without warnings, after that player has been warned several times in the past for the same reason.
All in all
Yes, when someone is lagging, doesn't matter how much lag, the game doesn't drop in fps or anything, so you can't know, unless you check your ms, or when the player count is low, and you see people warping.
Right now checking your ping won't do much, because the player is too high to let someone know if it's them or the server.