I too like @ralphm’ idea of listing topic title in the PM, but I am concerned that his proposed message is too short. The current message explains that it was hidden by Akismet (though it doesn’t say what that is), and I think that is important. Here is my proposal (basing of of current message and @ralphm’s proposal):
Thanks for your recent post contribution!
Akismet, our automated spam filter, has temporarily hidden your post in [insert topic title here] as potential spam.
Please be patient while a
staff member reviews your post; don’t be concerned as this is an automated process, and please note that submitting your post again will not expedite this process.
If no issues are found, your post will reappear shortly.
We apologize for the inconvenience, and thanks for being a part of [insert discourse name here]!
My biggest point would be to mention is some way, shape, or form what Akismet is without making someone (many times a new member) click on an unknown link. I can speak from personal experience that when I first joined the discourse where I now moderate, I was very confused by this message, especially not know which post it was referring to. This may not be the case on other’s sites, but personally we have found very few posts which are actually spam flagged by Akismet. If memory serves me right, there have been ~90 posts flagged, of which 3 were spam.