First, I don’t know the specifics of this particular message or why it was deleted. (Very few TMC moderators have privileges over the entire set of forums, and I’m pretty sure this wasn’t in one of “my” areas.)
We actually do delete posts for a number of reasons, the most notable recent is spam on the boards. Other might be duplicate posts, excessive cross-posting, or clear mistakes. In general we prefer to move posts to quarantine threads rather than deleting them outright. Writing a post that a moderator disagrees with is not, by itself, grounds for being deleted. People write all kinds of things in forums I moderate that I totally disagree with, but as long as they follow the forum rules, their posts remain.
You’ve been on TMC for years (longer than I have in fact). I personally wouldn’t take a single post getting deleted as conclusive evidence of a change against years of precedent. And we haven’t had any changes in moderating policy in the short time I’ve been involved with moderating.
In the best case, whichever moderator deleted your post (who was, again, not me) might reach out to you to explain further.
Bruce.