In your case i guess its okay - at least not the worst type of teamkilling
.
BUT there are some "hidden" problems (and thats the reason why some admins do react) :
Teamkilling/-wounding is against the rules.
Also this might give new players an idea of teamkilling being tolerated - which it is not.
If everyone would tk his clanmates at the end of a round, it could sometimes result in a lost, but most likely in a delayed round.
Once started, teamkilling sometimes goes completely chaotic and spreads to other players.
And sometimes admins don't get that it's a clan intern, funny, trolling tk-duel.
Just stick to the rules when you face strangers - but never forget to troll a bit with your friends and to enjoy yourself.
IMO too serious players are worse for the game than trolls are.
Also, you can always ASK admins ingame if its gonna be tolerated or not.