Sure, it is a bad workwoman who blames her tools, but sometimes the tools do not behave themselves.
I am having “fun” today trying to get a version of Salon Futura that I can put on the Kindle. Mostly this involves stripping out all of the nice formatting and graphics from the EPUB version because the Kindle doesn’t support it. But one thing it is hard to get rid of is the need to highlight text in some way, for example when you include a quote.
The list of formatting commands that the Kindle supports is quite limited, but there are things you can do. Unfortunately the Kindle is also quite bad at supporting CSS, so most of your formatting has to be done by hand in the HTML. This is a pain in the butt.
Except that Sigil, bless it, knows better than you do. It doesn’t like inline formatting in the HTML. So if you add such commands to your source in Sigil then the program will create styles for you when it saves the source, and consequently the resulting code still won’t display properly on the Kindle.
Yes, there are ways around the problem, but really software should be better than this. No wonder so many ebooks are badly formatted.