[KevinH]

Again, not a bug. Prettify works on xhtml content as designed. You need to add xhtml pre tag if you want to protect its contents from having whitespace modified and to be semantically correct you should probably be adding the code tag given your contents.

Again css can be used to pre-wrap whitspace, make an inline tag block, or make a block tag inline. The Prettify routine in Sigil ***ignores*** all css on purpose since css can change how normal tags are defined. So use the "pre" and "code" tags in xhtml to protect regions from whitespace being changed in Prettify, or just use Mend without Prettify.

There are other ways to deal with it but if all you want to do is indent a line, then define css for that line and provide a suitable text margin.

I personally would consider a series of non-breaking spaces to be a poor solution when pre tags and css exist to handle your case properly if you feel you must run Mend and Prettify instead of just running Mend.