Comments sent by anyone other than a logged-in member are moderated before posting, usually within a day. Comments, if any, that don’t appear to constructive are visible in each article’s “shadow thread” visible at the bottom of the comments with a “click *here*” link. If your comment appears in neither place within a couple of days, it was a false positive for the spam detectors, and fell afoul of the automated spam filter. In such a case, please rephrase and resend.
See below for an example of a hidden comment.