You probably sent something stupid or harassed someone over PM and got reported.
The only messages I send are to my friends. If I do send any to people I don't know, chances are they PM'ed me first, and I replied. That being said, I have said some questionable things, but it was all in good humor, and they were sent to good friends of mine. We were probably just having a little slap-fight via PM and one of them got a little angry. Every friend I've made since I've started playing Blockland is still my friend, minus a couple who were just plain idiots and shouldn't have been my friends anyway, but I've never PM'ed them.
tl;dr - If I've said anything unreasonable via PM before, it was all in good humor and the recipient(s) and I are still on good terms.