Noticed this in a competitive match on Trainyard last night; I tend to spam health packs for my team as a matter of course. After we were all killed and pushed back, I received health bonus XP notifications from players on the other side twice; one for 11xp (woo!) and another for 582xp after that player planted C4.
I’m guessing that I shouldn’t be receiving XP for helping the other team. I don’t have a screenshot but can try to get one if it’d help.
I see this is in the patch notes for the October update … you’re welcome.
:’(
Well, today, this happened again (After the october fine-bugging update). I was playing Aura, and a Rhino killed me. He started to finish me but I pressed the space bar (redeployment) before he could finish. I nevertheless had a 10xp healthpack bonus. Seems like someone forgot to check it thoroughly…
That one might have been left intentionally because it’s so rare for a rhino to be given health by his own team (based on personal experience) 
Yes, I know, and you are not supposed to gain XP from it. I mean, gaining XP by helping the enemy team? That was my point. They fixed it, and forgot this specific case. Typical 
I gave an enemy proxy a health pack via her looter perk and definitely got 10 support xp from helping the enemy.
Add it to the fix list gang!