If you rename a topic you break gmail threading, leaving a discontinuous conversation view in gmail:
We try to keep continuity by including the
Refrences headers (which are matching in both emails):
In-Reply-To: <firstname.lastname@example.org> References: <email@example.com>
But… Gmail is just being silly:
Currently, this is not possible with Gmail. It uses the subject line as the unique identifier of a conversation and nothing else. A lot of people have been requesting this feature for several years however.
This is not going to change any time soon, the issue has existed since 2010
I think this is one of those rare cases where it is worth adding a setting just for GMail.
[x] retain original topic title in email notifications
Given how predominate GMail is I would go as far as to say it should be default on, even if not it should be a user option.