To conclude for me, to get consistent results with Sigil 0.4. Beta, I followed DaleDe hint (
I think it was the <b> that gets you in trouble.) and selected on a permanent basis the following tags in W2X which now work quite well with Sigil, even for bold-italics:
Bold:
<strong>
Italics:
<em>
Superscript:
<sup>
Overstrike:
<del>
I chose not to implement anymore
Underline as they say in W3Schools.com "It is not recommended to underline text that is not a link, as this often confuses users."
Thanks for your help and patience.