[DiapDealer]

I (and I suspect Kevin, as well) would love to be able to support the use of the unicode character for the nobreak space in Sigil. The current parser (Google's Gumbo) could handle them just fine. Unfortunately, the unicode character cannot survive Qt's QTextEdit environment, which Sigil uses for Code View/Book View. They get changed to "normal" spaces. Hence the entity to keep that from happening.

Kovid has found a way around the Qt issue in calibre's editor, but he has the advantage of not having to deal with--by his own (wise) choice--a WYSIWYG Book View in his editor. We're not so lucky. We've inherited Book View.

We hope to be able to utilize the same kind of workaround technique for this issue, but while a WYSIWYG Book View editor is a part of Sigil ... it's not likely to happen (unless Qt miraculously chooses to support unicode no-break space characters in QTextEdit someday).

Until then ... both Sigil and Calibre's editor can handle each other's content just fine. If you use both, you'll just have to accept the fact that your no-break space entities may change (and calibre's no-break space characters will be converted to entities in Sigil. You can easily change them all back to characters in Calibre).