I'm perfectly TS open. That doesn't mean that I do it on every character I have, but if my character is down for it, then I am generally down for it too. Unless I'm not, in which case I'll just suggest we fade-to-black instead. Usually this is if the other person wants more of it than I do, and I'm more interested in getting that stuff over with so I can focus on the plotty or character growing stuff (which TS can certainly be part of, too, but not the 3rd time in a week.) One of the people I most enjoy to RP with hardly ever TS, but if the story takes us down into a romantic (not necessarily romantic romantic), we'll just fade to black on it.
Once or twice someone got overly attached, and projected the IC romance onto my OOC self, in which case I'll say I don't feel it's okay (it depends on the level of it). One time someone wanted to do shit I had no interest writing, and when I said it was cool that the characters did it, but I saw no reason to write it out, and s/he blew up on me, and I just extracted myself from the situation.
If people have boundaries, respect 'em.
I don't think I've ever discussed ts style with anyone, nor do I think I'd see much point in it. My TS writing is just an extension of what I write all the time. While there have been times that I've absolutely not been into the style of whatever partner I'm writing with, I never really felt it was my place to suggest they do it differently. I don't think I'd feel all that psyched about someone unsolicited directing me to write differently so they'd be more into it, though I suppose it depends on how they put it.
All that said, I'm pretty much on the second person bandwagon. Don't do it.
Edit to add:
- I mostly play it by ear.
- I write pretty explicitly in my regular writing, so my TS is the same.
- Never stopped playing with someone over TS. Its never been too little, and if its become too much then I'll just Fade-to-black. I assume my opposite side'll let me know if they think its too much.
- Discuss limits if you have them, when you think things might veer into sexual territory. Generally there's an escalation, at least in my experience.