For the most part, no, you won't find members/attendee's of Kumori Con using the IM links for abuse.
But there are always sleaze bags on the internet, and Kumori Con can't police every single person who even looks at the Kumori Con page. If you are worried about further abuse, you could just take down your IM link, and pm your IM name/s to people you think need it, or friend personally.
And, of course, block said abusive user.
But, all in all, Kumori Con is a MUCH friendlier Con than most.
Hopefully the IM wasn't because of mistaken identity, you'd be surprised how friends greet each other sometimes. ^.^; (I once thought a member of a different forum was a close friend of mine, and it wasn't until a month later I realized that the person wasn't even related to my friend. ^.^; )