Andy,
The same few keywords are repeated over and over again until finally one of them, "professor" is cut off as "profe". PM always removes redundant keywords on display so PM shows the keywords as "academics, classroom, faculty, ian helfant, lawrence hall, professor, russian and eurasian studies, fun, profe". The last keyword is not the same as "professor" so it is included. If PM were to update the metadata, it would remove the redundant keywords (I just tried it and it was reduced to the displayed set of keywords, including "profe".)
The file was created by C1 (I see it in their creator tag) so I think the problem lies with it and not Photo Mechanic. It may be that having multiple sources of metadata (embedded IPTC, embedded XMP, and sidecar XMP) is causing problems for C1. You could always try going with a pure XMP-sidecar workflow in PM and see if that helps things. PM still offers to embed IPTC but it is an all but dead metadata format now that XMP is well-established.
HTH,
-Kirk