Since pretty much everything else can be previewed before submitting, I'd find it handy to be able to preview artist commentaries as well. I tend to put in Note-style formatting and have to change it to DText afterwards, since there's no preview function.
In addition (or alternatively), I'd find it helpful to have a "Commentary description (but not title) is formatted using DText" note in the Artist commentary box, similar to the one under the forum topic input box. This is mentioned on the help:artist commentary page, which is linked from the Artist commentary input box, but having it mentioned directly on the page while adding the commentary would be handy for translating.