Is someone refusing to claim in jail (in ranked) reportable? It's obvious throwing. Learning to claim to jailor is something everyone learns in classic, so not claiming in ranked is obvious throwing. If it's not reportable, it should be, for the following reasons.
1) As already said, by time you get to ranked, you know to claim to jailor.
2) Jailor is confirmed town, so again, no reason not to claim to them.
3) People use this to throw, then subvert blame to jailor.
4) People use this for the above reason, but also to harass jailor and get town to harass them as well.
5) They could be afk, which is also reportable. Unless they have a good reason, like their dog peed on the carpet or something worse, this isn't an excuse.
Reasons not to:
1) They might not realize they have to, except I'm only asking this for ranked, where everyone knows that already. It's a basic part of the game that you easily learn after 50 games, so this isn't even an excuse.