I created a new Bitbucket project and repo. I cloned the empty project, dumped a codebase into it, committed it, and pushed to the server, using the Eclipse Egit interface. This all worked fine, but I noticed in the commits list on the Bitbucket web site, the "Author" column was not my regular login uid, but a "service account" that I've created for some purposes in the past. I checked my "git config" (both repository and global), and there is nothing that refers to that service account. There is also nothing in my Eclipse preferences that I can find that refers to this service account.
I later made another change on a branch, pushed to that branch, created a pull request, and merged that pull request. The "Author" notations for those changes are almost all correct, using my actual name and userid, only the commits have the wrong userid.