If an editor manually enters a signature using four tildes, discussion tools recognises this as a signature and doesn't add a duplicate (although see also T278355). However if a user adds three or five tildes (most commonly due to a typo) the whole signature is added again.
Steps to reproduce:
# Reply to a comment (or start a new comment) using discussion tools
# Write any comment followed by either exactly 3 or exactly 5 tildes (e.g. `Testing. ~~~`, `Testing. ~~~~~`.
# .
# in visual mode: Save the comment
# in source mode: Save tge comment or view the preview.
Expected results:*
* In all cases: Testing. Thryduulf (talk) 17:15 24 March 2021 (UTC)
Actual results:
* Three tildes, in source mode: Thryduulf (talk) Thryduulf (talk) 17:15 24 March 2021 (UTC)
* Three tildes, in visual mode: ~~~ Thryduulf (talk) 17:15 24 March 2021 (UTC)
* Five tildes, in either mode: 17:15 24 March 2021 (UTC) Thryduulf (talk) 17:15 24 March 2021 (UTC)
*There are infrequent occasions when an undated username or only the date (or very occasionally, an unsigned comment) are desired, so an option to override the automatic signature on a per comment basis would be absolute perfection. However, that would add complication for a rare scenario, with the option of using the old fashioned method always (I hope) available so (what I guess would be) the large amount of work required to add this is probably not justified, therefore this request is only for three, four and five tildes to give the same output.