I recall a time when "manlet" was only used on sites like 4chan or building forums. Anyone who used it elsewhere would be told to go back to those places.
Now, however, I've seen it used everywhere. Generic message boards about video games, music, dating, etc. It's all over YouTube, Twitter, Reddit. I also remember when only guys used this label, but now, I've even seen girls saying it to be hip and "one of the boys."
Short men are also being told to call themselves this, often by fellow short guys, because it shows a
good sense of humor and pride. I just find that humorous, since I've
never seen people telling flat girls to call
themselves ironing boards, or fat women to call themselves landwhales.
I'm just now waiting for the day it's used in real life. I remember "gaylord" being parroted in school because kids found it hilarious, so nothing would surprise me now. Currently, we're at, "nobody would say manlet in real life, it'd be too
weird." That's what they used to claim about saying it outside of specific websites. Look where we are now.