This is a reference to "malthe/chameleon#327". It is here just to inform PageTemplate users about the issue.
The behavior makes the analysis of template problems more complex: instead of a precise error message "the start tag in line ... lacks an end tag" the result can have several kind of errors, such as missing content, NameError -- not all of them easily associatable with the problematic tag.
The issue can be closed as soon as "malthe/chameleon#327" gets closed.