I'm sorry about my slow response. The good news is that we've tracked down the problem; the bad news is that the solution has significant ramifications.
Here's the thing. Bitbucket has always been extremely eager to match every commit to a Bitbucket user. Too eager, in my opinion. Any committer string which conforms to the Mercurial convention of First Last <e-mail> will be handled correctly. If our regular expression does not find an e-mail address in a committer string, we look to see whether there is a Bitbucket user whose username matches the entire string.
That's the case here. Someone committed a changeset as "chip" and pushed the changeset to Bitbucket. Bitbucket incorrectly attributes the commit to you, which is why it appears in your newsfeed.
The solution to this problem is to continue to match e-mail addresses and to continue to respect any aliases specified, but to stop matching committer strings with Bitbucket usernames. The reason we can't immediately flick the switch, as it were, is that many users take advantage of this eager matching.
We'll come to a decision and roll out a fix in the not too distant future, as we all agree that the current situation is unacceptable.