I filed a request for enhancement about using bracketed prefixes in subjects as filters:
Barry mentioned that I should raise the issue with regard to the dlist discussion, I presume because my proposal overlaps and/or conflicts with it.
However, the only things I know about what a "dlist" even is has been garnered from skimming the four messages on the topic in the archive, and it's not clear to me they my idea is necessarily compatible with dlists. (They seem to be exclusive proposals that may handle the same usecase.)
I've only just subscribed to this list to participate in this discussion, and my knowledge of the inner workings of mailman is fairly limited.
But I present to you the contents of the RFE I filed, in order to facilitate discussion:
Many large mailing lists use bracketed prefixes in subjects as a way to filter messages into smaller buckets, allowing some subscribers to read all mail sent to the list while allowing others to filter messages (in their mail client) to read only the messages they are interested in.
For example, the W3C's www-style mailing list uses these tags to filter messages based on which CSS spec they refer to. Thus, a subject line that begins "[css3-fonts]" will be assumed to be about only the css3-fonts spec, with a target audience of only those interested in that particular spec and not, say, the css3-flexbox spec (whose subject lines would be prefixed with "[css3-flexbox]").
To handle this, the Mailman archive interface would provide an option to filter only on particular prefixes (as well as messages that don't have any prefixes), allowing a user of the archive to use it as they otherwise would, but filtering the output such that they only see the messages they want to see, instead of the whole archive.
In addition, it would be helpful to allow mailing lists to automatically prefix subject lines when the message is sent to an e-mail address using a plus alias.
For example, sending mail to firstname.lastname@example.org would prefix the subject line of the message with "[css3-fonts]" in the message sent to subscribers and in the archive, whereas sending mail to email@example.com would prefix the message with "[css3-flexbox]".
It should also be allowed to have multiple prefixes on a message, and having such messages be treated as if they had any prefix individually. In terms of plus aliasing, there are two ways to handle it: (1) allow aliases to specify multiple prefixes in a plus alias using some separator (e.g. a comma: www-style+css3-fonts,firstname.lastname@example.org); or (2) detecting and intercepting when a single message was sent to multiple e-mail addresses with different plus aliases for a single mailing list (e.g. sending the same e-mail to both email@example.com and firstname.lastname@example.org), treating it as a single message with multiple subject prefixes when sent to subscribers or stored in the archive.
Now, I understand that this is likely a huge undertaking, but I think it would go a long way to helping users with large and diverse mailing lists.
[EDIT: It appears the W3C may not actually use Mailman. But my point is still the same, so take my usage of W3C e-mails as a hypothetical example, if necessary.]
(My first thinking on the matter arose when dealing with the WHATWG mailing list, which I know uses Mailman. I don't subscribe to any W3C mailing lists right now, so I didn't realize that W3C may not use Mailman; it was only my use of the W3C archives that prompted me to file my original idea as a Mailman RFE.)