I don't think it's a rigid rule about being "all about hair".
Anything even remotely connected seems fine to me,
like humour, ideas, chat between members, anything that there's
a point to.
Like i've just posted a reply to idk's post
"Stories with rapid and extreme hair growth"
My reply contained no links or pics,
just a crazy but vaguely possible idea
for speeding up hair growth by using time travel !