thinking about all possible optimal reasons to attack your own pokemon. reply with ones I miss
1. self u-turn / volt switch to reposition
2. Adjust HP distribution among your two pokemon
3. lower partners HP to eat berry
4. self proc weakness policy

5. trigger an ability
6. fling a beneficial item
7. knocking out your own pokemon to get a switch in while trapped
8. knocking out your own pokemon to gain a different advantage (reset fake out / get beast boost)
9. thaw partner with a fire type attack

oh and who could forget the most important one: taunting your opponent by showing you are so far ahead and locked into a win that you can attack yourself just for fun (don’t do this one)

one clarification, I was only considering actual attacks rather than status moves, but thinking about the possibilities there is fun too!