So, this is a feature that many, but not all, communication platforms have. I would like an option to view if a user has “read” (seen) a PM sent to them. Facebook Messenger is the most prominent service that does this, and I believe Google Hangouts and Skype provides this as well. While I do not want to see this in regular topics (too messy), PMs are generally small enough where this would be a nice things to see.
However, I am torn about whether this should be available to all users, or just to staff. The recent example that brought this feature to mind was a user publically complaining that their post was flagged and hidden. As the moderator who flagged - and then preceded to hide - the post, I flagged the post again and sent the user (and
@moderators) a PM explaining why I hid it (the link posted http://lmgtfy.com, violates our site guidelines) and asked the use user not to post that type of link again. While multiple moderators have liked the PM, the user has not, and I have no way of knowing if he has even seen the PM. So that is the moderator use case.
As for a regular user, I think the use case is similar (know if your message has been seen), but not as needed. Additionally, I am not sure how users would react if they know others could see if their messages were read, even though they are PMs.
Further, the ability to customize the “edit the post please” PM would be great, but I will create another topic for that per Meta rules.