I think this is a server configuration issue, because it's only happening on one of my hosts, and I haven't found anyone else with the same issue on another host. But I'm asking in here in case someone has seen this behavior before.
When I set a deleted WordPress post to return a 410 "gone" error, by adding code like this to htaccess:
"Redirect gone /post-slug-here"
On most hosts, it returns the Apache 410 page, like it should. But on this one host of mine, it's returning the standard WordPress 404 error page. Which gives the search engines an entirely different message, and not the one I need them to get.
I trouble-shot this by removing all rules from my htaccess. Then I put back in the 410 rules only, and it went to the Apache "Gone" page like it should. Then I put the standard WordPress rules back in, and it started sending 404s. To me, this suggests that particular server is having a small config clash with WordPress' rules. There must be something in the server config that's not quite right, and once we find that and fix it, all will be well.
But I'm having enormous trouble getting my host to understand this. Am I wrong about the cause of this issue?