I'd allow Kender. I wouldn't allow disruptive play. The player would have to figure out how to do one without the other.
Yeah, this has been driven home in my recent Dragonlance game.
I'm playing a gnomish wild sorcerer. And gnomes on Krynn are the "mad scientist blow everything up" kind of comic relief. Which is different than the kender's style of comic relief, but no less insufferable when you are actively hurting the party and screwing everything up with your love of explosions.
But my gnome is NOT the biggest annoyance in the party. Sure, he's a wild sorcerer - and sure, he might blow up the party someday in a fireball (though so far, he hasn't been that destructive). And he's not exactly a
reliable party member. But he works fine with everyone else, doesn't really get in the way, and is surprisingly useful (even to me!) most of the time.
That's largely because of my choices as a player. I want to play a gnome wild sorcerer, but I don't want to make the game less fun for my fellow players because of it.
At the same time, our game has an elf ranger in it. DL elves are, apparently, one pointy-eared goose-step away from proclaiming themselves the Master Race, and this elf is constantly, begrudgingly, accompanying the rest of the party. She's always throwing a fit about something or other. She refused to put on a disguise for an infiltration mission (because elf?), she has healing spells but you wouldn't know it for how often she helps people who are injured, she has aimed her weapons at other party members multiple times (one time she was mind-controlled....but only one time...), she has no qualms about triggering area effects when allies are in the way, she disregards the other party members when choosing targets (she's gone for targets that were harmlessly asleep or incapacitated over targets that are actively harassing us).
This player seems to be more....struggling....with playing his character in a way true to her personality, but also in a way that doesn't disrupt play. We've managed pretty fine so far, but the character's always a few inches from just being written out of the story because she refuses to be part of the team.
It's not the kender that is the problem. Though they might be attractive to players who are more likely to be problems, the problem lies in the disruptive player (or the player who can't make the race constructive), not necessarily in the race itself. I could be a CRAZY disruptive gnome wild sorcerer. That elf ranger could NOT be so disruptive. That boils down to player choices in character actions.