When a commons user went to edit a section of [[Commons:COM:SCOPE]] they got a fatal exception (Actual exception text courtesy of Reedy. Stack trace attached) :
2013-10-27 14:18:21 mw1050 commonswiki: [4672fc92] /w/index.php?title=Commons:Project_scope&action=edit§ion=13 Exception from line 77 of /usr/local/apache/common-local/php-1.22wmf22/includes/parser/StripState.php: Invalid marker:UNIQ7fcfb94d3c323dfe-h-0--QIN
(Presumably somewhere along the exception logging code, the \x7F actually gets treated as a backspace, removing the leading space and the trailing U).
Give that \x7fUNIQ7fcfb94d3c323dfe-h-0--QINU\x7f is a valid strip marker (provided that 7fcfb94d3c323dfe is the correct magic number), this raises somewhat of a mystery. Suggests that maybe something is calling $wgParser->parse somewhere inbetween from a hook or something.
Although everyone seems ready to blame translate, filing in mediawiki as translate doesn't actually appear in the stack trace, so not a lot of evidence yet.
(as an aside, this can be reproduced by putting the exact text from the stack trace into special:expandtemplates. Thus far I have not been able to reproduce locally. Still investigating)
Relavent links on wiki: https://commons.wikimedia.org/wiki/Commons:Village_pump#MediaWiki_error_message_when_editing_Commons:Project_scope ( https://commons.wikimedia.org/w/index.php?title=Commons:Village_pump&oldid=108125046 )