for example that an individual using option 1 hurts everyone else, while option 2 is neutral in that regard.

I think that is actually a huge distinction, not a minimal effect.

That's not even the full extent of it either. Self-voting is "sticky" in a way that burnpost is not. Someone voting for burnpost need only see something with some sort of vaguely positive value to rationally decide to vote for that instead, but a self-voter won't because they would be giving up their own rewards.