Rejoining is only against the rules IF they gain levels or play the same round twice. Max handicap is level 15 so unless you play the same round, rejoining past that isn't against rules.

I have to agree with Ibiza here, 3 day for connection spam is very excessive considering he didn't know and couldn't be warned that it was spamming the server. It's not like he was banned several times for connection spam before so his past bans shouldn't really matter with something this small of offence.