To clarify: While I was using my Astrologian abilities/cards around my base to level up my skill, my friend from maybe fifty blocks away who was doing their own thing(not even necessarily looking in my direction, even) mentioned that they had card visuals randomly popping up around their character. They were not a target of the spell, seeing as they were so far away, nor was I aware of this issue until they said something themselves. Everything appeared fine on my end, so it's probably a client issue or something.

If it happens again, I can try to get them to take a screenshot of what happens when I cast a spell, and figure out exactly how far away they were. I suspect it has something to do with being within view distance of another player, but I'm no expert or anything.