This article is from the rec.music.reviews FAQ, by Al Crawford (email@example.com) with numerous contributions by others.
No, none whatsoever. Many of the more regular posters to the group have
developed distinctive reviewing styles, but there are no restrictions
on presentation other than that the text be reasonably neatly laid out.
Try to ensure that you break lines in a reasonable place (not everybody
has a 500 column screen) and that you don't type entirely in capitals,
which can be difficult to read. It's also helpful if your review has a
reasonably descriptive subject line. No subject line or a subject line
that reads "A Review" won't get your article rejected, but it's
certainly preferable that you include an informative subject line