The only caveat I couldn't find a way out of it was... Gmail doesn't group messages with different subjects, even if they have the correct chained Message-Id and In-Reply-To field.
So, if the first subject is: [Friendica:Notify] #649 Comment by Mike and the second is [Friendica:Notify] #649 Comment by Abinoam
(Same #649, and correctly chained by Message-ID and In-Reply-To) They will not be "threaded" at GMail, and I guess it'll not be threaded on other mail softwares.
So, I think the "anonymous" notify subject should be the default. The other way should be enabled by an "option" or a plugin, I think.
If we can't please both sides, we need to provide an option. I'm a little hesitant to recommend that the default option would be to leave out important information from 'system notifications'.
My own choice is to provide the more detailed information.
I've been pondering this a lot. Here's my current thinking...
I personally miss the "xxx commented". "Somebody" just doesn't convey enough info.
Putting the number inside the brackets makes it harder to filter with mail filters.
So here's my plan - I'm right now adding plugin hooks to the enotify function. I'd like to put back the names by default.
And threading these based on references: works on "real" mail readers. It seems only gmail ignores the threading headers and forces a subject line match.
So I propose a plugin which can alter the subject line in the notify emails either for privacy or for Gmail threading or both.
Also Simon I believe the issue with the privacy of the subject line is that these are visible on your mail reader screen even if the message isn't selected. It's like the N-S-F-W plugin - there are times when you might not want to have the names of certain people appearing on your screen and we should accommodate this. But "somebody did something" doesn't seem very informative and it shouldn't be the default.
@Mike, the "xxx commented", when properly threaded, is really more pleasant than "somebody commented" (I tested it in Thunderbird). The other way, to have ALL comments by one person threaded together on GMail is making some "conversations" (threads) to have more than 50 messages (and growing). So, I agree with you. Default to "xxx commented" and plugin to "Somebody commented".
Have now cleaned up the subject lines, restored the default - (naming the commenter), and added a plugin "gnot" for either anonymising these notifications or threading them on Gmail.
They will look like
[Friendica:Notify] Comment to conversation #47990 by Mike Macgirvin