What do you mean "rule of thumb"? That's just an old meme making fun of how most Internet users were male. It's not about how you shouldn't mention gender.
If gender is never mentioned, maleness is assumed all the time, and then male users will not realize the abilities of their female peers.
I think something valuable is lost if everyone must present irrelevant identity information to combat false assumptions some may hold. At least for the crowd who want to primarily be associated with attributes that can be merited to their choosing.
If gender is never mentioned, maleness is assumed all the time, and then male users will not realize the abilities of their female peers.