The majority of the games i have played today have ended with one of my team mates self destructing all commanders, not only is it impossible to figure out who did it in a team with more then two players but even if manage that there is no way to provide any evidence with enough weight to actually report the player to uber. Planetary Annilation is in a despret need of a player report system and a system that records enough information to prove guilt.
I think the game should at least say something like "Commander self destruct initiated by $teammate. Cancel Self Destruct? Y/N" and give you a few seconds to cancel. Maybe even a team vote. Plus then you will know who did it, and can avoid playing with them if you choose to in the future.
From what I know of the game mechanics, it might be worthwhile for them to much more simply disable "delete" on the "commander" unit in team games. Still take a little programming, but the least of all solutions. In a team game, if you want to delete your commander, deliver it to your enemy with an astraeus or something.
If people want to self-destruct all their teams units, then preventing delete on comms won't stop them. It's an inherent problem with the shared armies game mode - it's excellent for pre-made teams but there's not much you can do to stop trolls without compromising the fun of shared armies for everyone else. Even with all delete function removed (something that would itself be incredibly annoying) people could still just cancel other player's commands, suicide units etc etc. I've had to deal with people rage-quitting as well and I can't think of any solutions beyond not playing shared.
Who Deleted That should be built into the vanilla game. You should also not be allowed to delete a large amount of units at once and you should be prevented from deleting Commanders unless you are the last person still playing on a team shared game (everybody else on your team disconnected). I am really surprised this hasn't been done yet.
I would recommend getting more reliable team mates, perhaps by joining a clan (Realm advert), or by using one of the many PA-related chat groups (I think one plug is enough for this reply ). That way you can be more confident your team mates aren't going to screw you over by deleting commanders, you're more likely to learn how to get better at PA, and you might make friends and be happy and emotions.
Just disabling commander self destruction does not really adress the core problem because then they will just delete all your structures/units instead.
One game i played had that, but it seemed to bug out or something because it did not show who deleted the commander.