[DiapDealer]

In all fairness: it's not really even a Sigil issue. Sigil works as advertised. Non-breaking space functionality is accommodated. No unicode non-breaking space characters will be lost. They're just converted to entities.

It's not really fair to expect us to overhaul Sigil's codebase merely because you want it to be easier to bounce back and forth between using calibre's editor and Sigil when editing your epubs. There's differences between the two programs. Utterly seamless integration between Sigil and calibre is just not one of our priorities (not that we seek to create stumbling blocks either).