"message counter" is using only one plural form/choice to display info about total number of selected messages and the number of unread ones within when I have two threads selected (needed to show summaries) with one unread message and some number (depends on locale and plural rules) of messages marked as read (in one thread) - in other words, we are using plural form of total for unread. Affected string: countUnread@mail/chrome/messenger/multimessageview.properties
Can you attach a screenshot to show which message counter you mean?
Confirming, I see that too with the latest Daily build.
Created attachment 696261 [details] [diff] [review] proposed fix Thx Stefan for the analysis!