Anyone in doubt that Mould can infect human hair may wish to visit the following URL. It gives a good introduction to Mycology generally, not just how it can affect Hair, Nails or Skin.
http://www.doctorfungus.org/mycoses/human/other/Piedra.htm
Whist at this site, you might also like to study the conditions that Moulds and Fungi most like to grow in.
If after reading this you still want to tie wet hair, fine, at least you have made an informed decision.
After looking over the site I have come to the same conclusion...
No such thing!
Let it go. This isn't an issue. Why make an issue out of a non-issue?
Having wet hair in a tail or braid does not allow hair to get moldy, especially since it'll be wet for hours and not days, weeks, or months.
This is my last post on the dreaded "hair mold"!
now, hair mold could be a shaping device like a jello mold for the head. then you're dressed & ready to be a really fungi. heh.