I don't think it's possible to hide latest post notifications from just one thread.
Historically, all posts in the Lounge here were excluded from latest posts This remained the case until just a few days ago. This was because the original CM deprioritised the Lounge, and prioritised the 'serious business' of bughunting. We made the decision to make posts in the Lounge appear in latest posts, as they inject some fun back into the forum and provide a way for mods and players to interact in a more relaxed manner than is possible elsewhere on the forum. Having those notifications helps newer forumgoers to find the 'fun stuff'. After all, we do want you to have fun, alongside the more serious beta purpose of bughunting
As Biloutte91 has said:
only one message appears each time in latest post
So this should not displace notifications from other areas of the forum too much
17 (I think lol)