Perhaps you've recently posted a comment or two -- or perhaps you've posted many over time -- that have never made it onto the listing page.
The most common reason, lately, is this:
Anonymous comments slamming hosts, open mikes, venues, other performers, etc. will not be published. *
They'll be ignored, perhaps ridiculed.
This is not to say anything at all is allowed if you're signing your name; but if you're going to be criticizing others, you'll at least need to stand by your words.
It's only fair.
And no, this does not apply to the vast majority of the site's users. So please don't worry too much about this notice. If you cared enough to read this in the first place, thanks for your contributions to and interest in openmikes.org.
* Actually, comments attacking other performers are unwelcome under any circumstances.