Last modified: 2014-03-10 20:30:15 UTC
If you change the contents of the last row in the table at https://test2.wikipedia.org/w/index.php?title=Private_Practice&oldid=56640 from "n-Perfluoro-Pentan C5F12" to e.g. "n-Perfluoropentan C5F12", <nowiki> escaping is added seemingly unnecessarily. My guess is that it's overeagerly trying to prevent a new table row (|-) from being started.
FWIW, I can't reproduce this issue locally in git master, only in prod.
This now appears to work in master – see http://en.wikipedia.beta.wmflabs.org/w/index.php?title=User:Jdforrester_(WMF)/Bug_52158&diff=83030&oldid=83029 – so closing as WORKSFORME. This was probably due to Parsoid's more aggressive approach to table wikitext purity back then. (Sorry for very slow triage.)