My apologizes to all who commented here recently and then had the comments disappear. The spam filter was acting up and suppressed many comments from ECN regulars. I restored them all now.
Update: Frank pointed out that his comments started being filtered out at the same time across multiple blogs. Here is what I suspect happened:
If an admin on any WordPress site, rather than deleting your comments, marked them as spam, then this feeds back into the Askimet database. (Askimet being the spam filter software owned and operated by the WordPress makers). Hence you’d be automatically filtered at every WordPress site that has this spam filter enabled (the default setting).
It is one thing to disallow some comments on your own blog, but marking something as spam, when it is not, has wider repercussions and is significantly more sinister.