If this has been mentioned before, mods please merge this into the appropriate thread.
When leveling costumes, the costume level is tied to THAT HERO ONLY. The levels DO NOT TRANSFER.
I thought I would be clever and level a duplicate 3/60 Rigard and allow my main+19 Rigard to serve active duty. This is what happened:
It’s not catastrophic, but DEFINITELY something to keep in mind.