E.g. http://jonathangiles.net/hello-microsoft/

See the '10d Comments' text. I believe this is an issue due to this line of code (refer to the %d towards the end of the line):
https://github.com/godaddy/wp-primer-theme/blob/45a92169c7cc8a6fbee65dba372593b4398f8f7d/templates/parts/loop/post-meta.php#L25

This appears to be a regression introduced by @EvanHerman as part of 45a9216#diff-a4a96713392ea0f2556a30370eccffb8