It affects the following items:

• log
• chicken
• shark
• steak
• fishy
• enemy corpses
• enemy crates
• enemy sponge - It should change ownership, see here
• enemy bucket - It should change ownership, see here
• Theoretically, a Dinghy, if placed in a catapult and the catapult is converted. - I think I fixed that here ages ago
• In theory, a Dinghy, if it is placed in a catapult and that catapult is converted - I might have fixed that here ages ago

Basicly anything that can be picked up and doesn't change ownership to your team.
I think items held by your team should not take damage even if the item is of a different team.

An easy way to reproduce this is by putting the item in a catapult, and shoot at that with another catapult.

Besides catapult rocks, this issue happens also with own team's Ballista bolts and a few other damage sources (bombs, drill, keg), but not with pickaxe, sword, boulder, arrows, dropped spikes.

I will address this issue soon.