Can someone else check that the following is true please? Maybe its dictionary or preference related.
The book I was editing had 4 xhtml files, of which I had one open in codeview. I corrected a multiple occurrence (12) spelling error via the
Change Selected word to button in the spell checker.
I immediately realised I made a mistake (corrected the wrong word), so I clicked in the codeview window and hit ctrl/z. Then I refreshed the spell checker, it reported there were now just 3 occurrences of the 'misspelt' word; the only changes that been undone were those in the file I had loaded into the codeview window.
So I did another test on the same book, this time I started the spell checker before loading anything into the codeview window, I did the same correction but this time I could not undo any of the 12 changes.
So I tried the same thing in Sigil, only to find it can't undo any changes made via the same button, irrespective of what's in the codeview window. So I went to Sigil forum to see if it was a known issue. I soon found that it had been had reported, just four days ago by calvin-c - it was the topmost thread!!
BR