Fixed in the current build.
When both cached and uncached comments appeared on the same page, uncached comments would inherit the line-break state of prior cached comments on the page. Since cached comments have line-breaks disabled because the line-break was already performed pre-cache, the uncached comment then also had line-breaks disabled. It would then be cached with the line-breaks not performed.
This was fixed by setting an explicit default state for line-breaks (on), rather than relying on an implicit default state (on).