Created attachment 174504 [details]
Same text with same style, plus direct formatting or not

I use LibreOffice 7.1.5.2. for Fedora workstation 34. My file's default language is French, and the languages of cells are defined by cell styles. I have 2 extensions installed and working: Grammalecte (French language grammar and spelling checker) and "Mongolian spelling and hyphenation dictionaries".

When I put some words in bold inside a cell by formatting them directly (selection, then Ctrl + B), then all non-English words or the cell are underlined in red by the spelling checker. Nevertheless, if I select any of these underlined words and go to Format → Character... → Font, the displayed language is correct.

I would of course expect that direct formatting would not affect the spelling checker work, so that only mistakes would be underlined, whether or not some words in the cells are formatted in bold.