To you what is the biggest sign someone online is a man pretending to be a woman?

For me it's someone who keeps turning everything sexual for no apparent reason. Like the OP asks a completely casual question, and they're just like:

OP: What is your favorite snack to eat?

Them: Why pretzels of course! I also just love when one of those pretzels falls down my boobs and I can save me a snack for later! 🤤

OP: What is your favorite outfit that you own?

Them: Oh not much... just this adorable black and white thong bikini that I own! 🙈 It's adorable how it makes all the boys around me blush! 😍

OP: What is your favorite sport to play?

Them: Oh basketball of course! I like how in basketball I get to run and jump around a lot and so I can watch my own chest go bouncy bouncy bouncy bouncy! Golly it's so much fun! 🥰

So yeah, you get the picture, lol. A normal person would just answer pretzels and basketball without all those unnecessary details. And they'd list out an outfit that isn't just swimwear.