[KevinH]

I just tried your test case and when I use a right mouse click on this html document and select Reformat HTML -> Mend Code. All is fine and no whitespace is impacted.

When I use a right mouse click on this html document and select Reformat HTML -> Mend and Prettify Code, it, as expected, will play with the whitespace of text within tags that are not pre or tt. Your are using css to give a "p" tag properties like a "pre" tag but the pretty-print code has no idea what your css has done or will do. So if you have changed the whitespace handling in other tags, do not use Mend and Prettify as spacing is important to you, only use Mend Code.