This is actually registered as a Moped, which I believe is classified similar to a bike and can be locked up on sidewalks. While that thing certainly doesn't look like a Moped, maybe it is, and it can be parked there. Sort of an eyesore and could be parked somewhere more discrete.

OK. But it’s been there for a couple of months, at least. I would say it is clearly abandoned.

I don't have anything invested in this, but it's got a high end, expensive chain securing it. I'd assume someone is just storing it there vs it being abandoned. Bet you, as well as they, would be real annoyed if the city came and removed it just because some random 311 person thought it was abandoned. I have a car I park in the city that I drove maybe 4 times a year...doesn't make it abandoned...