Team flashes have to one of the most annoying things on Frag Deluxe community servers right now. I can't tell whether this is due to a lower skill level of some players, simply not caring if you team flash people or griefing. I have some suggestions that could help with the situation (bare in mind I know very little in terms of what can realistically be achieved in the coding side of CSGO servers):
A flashbang ban, (similar to ESEA) this could either be implemented by mods for known team flashers or an automatic flashbang ban for the next few rounds if too many team mates are flashed by you
One flash per player, now this would suck because it is very hard as T side to do anything without utility but then again it could make it easier as you don't get team flashed when you try and peak anything
A black/white screen effect, what I mean by this is if a player flashes too many teammates at once their own screen would also be flashed to the same effect as the other players. Now I can see this system being abused by griefers but it was just a suggestion.
A ranking decrease, everytime a player team flashes another a notification pops up to tell oblivious players what they have done and showing a rank decrease to deter future team flashes
Ty for reading this and would enjoy hearing any suggestions or criticism to these points.