Thanks Becky, that's what I wanted to know. Anything involving more than a cursory change and it's better to run "Mend and prettify" as you said.
On the subject of sigil bs4 another oddity that I found is that I have this markup.
Code:
<em>Text with <strong></strong> an empty tag <span></span> here</em>
If i do say a <em> to <i> replacement in the plugin and just print the soup as string it will print as expected:
Code:
<i>Text with <strong></strong> an empty tag <span></span> here</i>
But if I want to indent the code and use the prettyprint_xhtml it will return self-closing tags.
Code:
<i>Text with <strong/> an empty tag <span/> here</i>
Now, Sigil doesn't complain about those. File preview works OK, saving the book has no problems and the moment you run "Mend and prettify" it will go back to this:
Code:
<i>Text with <strong></strong> an empty tag <span></span> here</i>
But I find it curious since those elements are not supposed to be self-closing AFAIK.