Ren thinks Crow is an interesting guy in general. It's amusing to talk with him from time to time without actually stressing about too much about what can be talked and what not. They don't know each other well enough for him to say they're friends or anything like that, but they're in positive terms. Positive enough for him to say that he'd help him if there would be a reason for that. And he's also keeping an eye if Cobra decides to take his ultimate revenge on Crow or something like that so he can warn him (anonymously or not).

Really, Crow's one of those people that you can just talk to in general which he appreciates since there's not really many people he talks to in general.

... and he's kind of used to the whole Mr. Casanova thing by now, so he'd be shocked if he one day called him by his real name (which I doubt, but you now... if). While he's tempted to just continue calling him Scarecrow, he probably won't use it as much as he could.