It's called trapping, and yes it's reportable, you won't get the tc back but he wil; be infracted but i don't see why you would report when you do it all the time...
GL on the report
Hello, I encountered a guy who wouldn't let me /spec from duels. Because when duel ends, he's very quickly join spectators and enter back.
That way he's forcing me to duel tho I'd like to quit. What's more, he uses the shovel opener. That's even worse.
I was wondering if such behavior is actually reportable or something?