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When there are several people in the TO field, all but the first and last are listed twice:
To: John Doe, Jane Doe Jane Doe, Peter Johnson
Note that there's no comma between Doe and Jane. Also Jane Doe Jane Doe has only one overlay.
Jane Doe Jane Doe
I checked in the raw message: no duplicated names there, so it is a display problem.
I'm using the development version of mu4e from a few days ago and GNU Emacs 188.8.131.52.
Correction: it also happens with the last email address in a list of several but not always. I haven't figured out yet what the pattern is.
Can you attach an example message that has this problem? Thanks.
I'll send one very interesting case to your email address. For privacy reasons I don't want to post it here.