I believe that a way to notify users of why the staff deleted or rejected their posts could be a useful feature.
That would avoid having to open a private thread or emailing them manually.
It could be a notification or a popup like when a user gets suspended.
It could be sent via email too if the user has mail notifications enabled.
This shouldn't be mandatory and shouldn't be available for standard users deleting their own messages.
I didn't find similar suggestions, so I opened this thread.

    9 days later

    This is not ideal, because the reason for deleting a message could be a private matter that should not be seen by others.
    Also, I believe this goes against the scope of that extension.
    We already use it for its intended purpose: leaving notes about the behaviour of users so that other moderators can see them and act accordingly when acting on that user. We do not enable ordinary users to see moderator notes.

    clarkwinkelmann use private discussions when a discussion needs to take place

    We do that but it's inconvenient when you just have to tell a user to open a thread elsewhere instead of commenting someone else's discussion (we have the approval extension too for the first comment and thread, but it can be useful for public comments too) or sharing some info like when someone asks us to delete their message and we can say "done!" in a simple way, or if someone flags a comment for something that doesn't deserve a public punishment but simply a little message to the user like "please don't talk about this topic".

    The notification could also follow a template that tells the user to send us an email if he wants to comment on our note. Maybe it could be done even for editing posts or without any connected action. Just the ability to send notifications like those received after being suspended. You can see it when you browse the forum and you receive it on the email if you have mail notifications enabled.

    That would be so easy without having to write an email or open a byobu.

          andreagdipaolo This is not ideal, because the reason for deleting a message could be a private matter that should not be seen by others.

          Moderator notes has two fields. One is for moderators, the other for that person. I don't think the text provided to the user is visible to others?

              luceos I don't think the text provided to the user is visible to others?

              I don't have the double field. I have it in the suspend extension.
              And I don't know if we run a modified version of the moderator notes extension, but users can't see our notes with this configuration:

              If users could see what we write there, the extension would lose its goal, in my opinion: it is for notes for the mods, non notes from the mods. At least I see it that way.
              But even if they could see the notes, I understand that users are not notified, they just can see it in their profile page.

              I believe that what I imagine is an entirely different concept, not fulfilled by any existing extension.

              Edit: https://discuss.flarum.org/d/23228-moderator-warnings-extension seems to do a similar thing but I don't want it to be necessarily linked to a warning or a strike. But I see that there is the 0 option. Could it be fit for our needs?

                  Oh, I also got the two mixed! I linked the Notes one but I was thinking of the Warnings one 🤦‍♂️ I had no idea there were 2 different ones...

                  The Notes are just on a profile, so wouldn't be useful at all for this use case. The Warnings are on posts, and there is the message for the user as well as the private message between mods.

                  If we can tell the user the reason for deleting the post when we soft delete the post, only the user and the administrator can see the soft deleted post and the deletion reason.

                  This is very friendly for forum management and will also prompt the user to know that I should not post such a post

                    meihuak But this can be already achieved by the moderator warnings extension when giving 0 strikes.
                    It could be done by a separate extension without the concept of strikes too, but it could be redundant.

                    That extension, however, is not perfetct, and seems not to be maintained