The reason that is being shown is that is the commit string that the individual committed their code to in their local Mercurial repository. They then pushed the changes to Bitbucket. The fact that the author is not hyperlinked means that Bitbucket is unable to determine which user that is.
This can be fixed by creating an alias for that person in your repository admin settings. We have recently stopped trying to do "magic" to try to determine who committed code. This was because we were attributing code to a lot of wrong authors.
The other way to fix that problem is for the user to verify that email address against their user account. This would allow Bitbucket to figure out who that user is.
I'm glad you're going all the way to solve this, thank you.
After your first reply I checked my BB account settings, and noticed my (Gmail) email address there had a "+bb" addition (modifying it to something like email@example.com), so my Thunderbird can redirect messages to the right folder automatically. So I changed it back to the original email address. But is that really necessary ? Put otherwise : if I enter a "+bb" modified gmail address, should my email address in Hg commit info in some BB repo still be correctly obfuscated ?
Second question : if I enter 2 or more email addresses into my BB account, will mails concerning issues like this one be sent to every address, or just to the top one ?