Text Previews

This one popped into my head before going to bed...

But what about adding text previews, for things like comments, page information and descriptions on stories and art?

Weasyl have it and its a really neat feature.

It allows me to view how my text would end up looking, in a small window beneath the actual window I'm writing in.

Meaning for instance, if I'm using markdown commands, like bold text, links, cursive, colored text etc. I get a chance to see if it actually works or if I messed up somewhere, where posting and having to correct it afterwards, by either finding out the command messed up on my own or being made aware if someone notifies me.