Reverted templates etc still show as modified

If I make a change to a template etc, it's marked as modified with the little m icon. However, if I use the revert button to set the template back to its original state, the template file is still marked as modified.

I live in fear of the day that support tells me it can't help with a problem because I've modified the templates, even when I haven't really because I've reverted the minor "will it work if I delete this class?" changes that were made for experiment's sake.

Shouldn't it be the case that hitting revert wipes out that modified status too?