Fixing Bad badEmail: invalid author/committer line - bad email in Git Repository

Question

I have a git repository I am attempting to move to github from bitbucket. This is something I have done before without much difficulty, both using the github importer tool and manually sending up a repo. In this particular case, however, my repository seems to have an issue in its history, which causes github to fail. Notably, when I run git fsck, I get:

git fsck
Checking object directories: 100% (256/256), done.
error in commit 18e86b4bdd4172bfca9f635abfedc84a8bf39bd7: badEmail: invalid author/committer line - bad email
Checking objects: 100% (90779/90779), done.

Git fsck seems to be telling there is a single bad commit, but when I look at this commit, I do not see an obvious reason why it is incorrect (e.g., perhaps a rogue hidden character in the email?). In any case, in order to fix this, the first thing I have tried is to rebase. The tutorial I have attempted to follow seems to suggest to grab the parent commit, rebase, then switch to edit instead of pick in the list. When I do that I am getting a merge conflict:

Auto-merging HourOfCode/SourceCode/Biology.quorum
CONFLICT (content): Merge conflict in HourOfCode/SourceCode/Biology.quorum
error: could not apply 18e86b4bd... Updated Breed method, IsParent method, added Tasks 2 - 6 sample code.

If I try to run the next commands in the tutorial anyway (typical amend commands), I get this:

git commit --amend --author="My Name <[email protected]>"
U   HourOfCode/SourceCode/Biology.quorum
error: Committing is not possible because you have unmerged files.
hint: Fix them up in the work tree, and then use 'git add/rm <file>'
hint: as appropriate to mark resolution and make a commit.

Now, I know I could just add the file, but given the impact rebase can have on a repo, it is not clear I have any of this right. I know if such a change goes through everyone will have to re-clone, but my question is, how do I fix this "bad email" into something acceptable and push up this history changing change without damaging my public repository?