When you open a ticket, you can write with the Tiki (and soon MarkDown) syntax in the "Description"... but you can't preview anything until you save/create the ticket... which is annoying trial-and-error, and everytime I have to "edit and try again" to try to correct some messed up syntax, then everybody gets spammed with an extra email for nothing.
Just like in wiki pages, or the comments editing field, there should be a preview tab (or even better, side-by-side realtime preview as an alternative to the WYSIWYG editor) so that I can see in realtime what I'm doing before hitting the Save button. I mean, it works for comments within a tracker item, I don't see why it couldn't work for the main description too.
You should also make that textfield 2x bigger/taller by default on desktop (non-mobile) versions, by the way. Scrolling a tiny textfield sucks, and it will suck even more with a rich text preview.