I haven’t seen that on damus. Is it a setting on a client?
nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z
If somebody is on my friends list why do I still get this ALERT messages? Is this a technical issue?
Repost if you like to discuss

Discussion
Post can be created with a content warning (not all clients support that). I did it for my 2 last posts for example.
Additionally some clients (like Amethyst) mark certain hashtags (like nsfw) with content warnings as well.