I have a Forsaken Rogue that I play on sometimes and have him show up in Alliance areas. However, I make it stupidly obvious he’s lurking / loitering and I’ll typically run off after a minute or two of causing mischief. I’ve had more than a few Alliance track me down on their Horde chars and ask me to come back, saying it added “flavor” to the scene to have a Horde rogue lurking about in the shadows. I was happy to oblige.
There’s a line just like anything else.
If you’re stealthing in the digital bushes trying to hide the fact that you’re there, it’s weird.
If you’re interrupting someone’s RP by forcing them to hear the whoosh of stealth every 30 seconds, it’s just annoying.
I’ve had people do it to me. Honestly, if you’re interested in my RP, just unstealth and sit nearby. I’d prefer it.