When there are multiple values for a single property, #ask and #show prints them in a comma delimited format, with 2 spaces after the comma. For multiple values entered into a Semantic Forms field separated by a comma and only 1 space, #ask and #show will insert a second space.
If there are no spaces in the Semantic Forms field, then #ask and #show will insert one when displaying it. That is (probably) the expected behavior. The problem only occurs when there is already a space separating multiple values. Then, the display of the values differs from the actual text of the output values, and leads to difficult to diagnose problems.
This breaks comparisons between properties. I discovered this bug using the Arrays extension, which removes the extra whitespace, as does almost everything else in MediaWiki-land and HTML-land. That's probably why it took so long to discover this bug - you can't see it without knowing it's there and deliberately looking for it. The bug goes back to at least 1.6, which is as far as I tested.
I will post a link to a demo in a few minutes.
Version: unspecified
Severity: normal