Please do not flirt with me unless you have serious intent or interest in me. I promise I won't bite if you do.
I don't want to be flirted with and then have it go nowhere, because teasing like that makes me feel super uncomfortable and it's like... what's the point?
Mild teasing is fine though, but only as an obvious shitpost or joke.
It probably goes without saying but only, or I will block you.