I recall a time when "manlet" was only used on sites like 4chan or bodybuilding 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 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 women to call
themselves ironing boards, or fat girls to call themselves landwhales. They can choose to do this, but there is no pressure.
I'm just now waiting for the day it's used in real life. Currently we're at, "nobody would say manlet in real life, it'd be too
weird," but that's what they used to claim about saying "manlet" outside of specific websites. I'm guessing this is because the kids and teens are now adults. An old man would probably scratch his head at this label, but a kid born nowadays in the Internet age would consider it normal.