IIRC any html, script and css capabilities were restricted to GMods, SMods and BAs
With the introduction of wbb4 that got even stricter and got changed to only me and noone else. I've played around with "html" editor a bit and so far couldn't find a way to do harmfull stuff with it that you couldn't do with the bbcode editor too. The functions are really restrictive, for example you can't use script and iframes at all, css is limited to some inline code, even from tables the row/colspan function got removed. And no idea why woltlab removed it, I just know that it made a bunch of people angry/mad.
The edittime is the same time the board blocks your from creating a new post in the thread, which is 30 minutes. That was introduced with wbb4 too as the board doesn't block you from editing your old posts after you posted again which lead to confusion.