I don't think keeping titles is so much an issue. The thing that stands out for me is that Flint will have dodged an automatic ban by doing things this way. Perhaps there should also be an automatic ban for a rebel leader if they abandon the realm during the course of a rebellion as well as for defeat in the capital. Either way he has led a failed rebellion.
But what Flint did in hanging on to a lordship? It sounds sensible to me. If you are a rebel losing a rebellion you don't hang around for the executioners axe! Though most times you will have no hope of leaving the realm in time to switch allegiance. I expect it's very rare and only in extraordinary circumstances that any rebel leader can make it outside of their realms borders before their rebellion is crushed.
