Bug 476606

SUMMARY
Please add an option to group messages by subject (preferably ignoring Re:, Fw:, Fwd: prefixes).

As far as I understand, the current threading option seems to thread by Message-ID and In-Reply-To headers, rather than subjects. In any case, in some cases messages with the same subject aren't displayed together. For most use cases, this may be right.

However, for some use cases, grouping by subject, regardless of the presence of those headers, is desirable. My use case is notifications from a forum about comments, with the subject of a notification being the subject of the thread; these are not replies to each other as e-mails, so they currently aren't grouped even if threading is enabled.

STEPS TO REPRODUCE
1. View / Message List / Aggregation / Configure...
2. Choose a mode
3. Go to the Groups & Threading tab

OBSERVED RESULT
No option to group by subject in either the Grouping or the Threading dropdown list.

EXPECTED RESULT
An option to group by subject, perhaps in the Grouping list.

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20231001
KDE Plasma Version: 5.27.8
KDE Frameworks Version: 5.110.0
Qt Version: 5.15.10
Kernel Version: 6.5.4-1-default (64-bit)
Graphics Platform: X11

ADDITIONAL INFORMATION
There are references to grouping by subject in earlier bug reports (Bug 313516), but it seems to have gone MIA.