Well, see for yourself:
On other sites that I checked the user names are trimmed, so it appears to be local problem with the Data Explorer site only.
Despite being fixed, the fix is still not pushed and the bug still exists.
Hmm, I had meant to fix that a while ago before anyone noticed, but I guess I forgot. At any rate, it's fixed in the next build > 2012.9.7.6 (may be a few days).