I tried to spawn a creeper in the City
I got disconnected by the server. It said Uncovery was notified. Will I be banned? Because I don't want to be. I would suggest that it says one is not allowed to place "object", instead of disconnecting, like it does not kick when one tries to throw an XP potion.
That has happened to several people, including me. If you only did one then no problem. I think if you tried to do a lot then might be a problem.
The kick is just to prevent you from spamming it. It is possible, though unlikely, that spamming the egg with a griefing client or similar means might actually get through the security check. Thus, it's safer for the server to simply kick you so you don't get the chance to spam.
It's a little inconvenient, but it's not hard to remember. You won't get in trouble for this happening by accident occasionally. Uncovery is notified so that if the logs show you are doing this constantly, you are probably trying to circumvent the protections, and that would be a likely ban.
Exactly. This is not something we haunt daon users that do that by accident or once and never again. But we have some noobs that think its funny to mass-spawn stuff and for those, the kick and warning is meant as a deterrent.