I wish they rely more on OS features, like the built-in, system-wide spell check. I know it's a bigger task for them, since Firefox runs on multiple OSes, but maybe it's worth it. It dreads me how “un-macOS” Firefox feels, and I guess this feeling extends to Windows, Linux and elsewhere.
In Windows-land everything is so inconsistent that it doesn’t really stand out like it does on MacOS.
97% of Windows users wouldn’t notice if it followed OS conventions and the remaining 3% would complain that it was following the current conventions instead of copying Word 2003 :)
Is it really that big of a task? More so than maintaining custom spellcheck dictionaries in every supported language? Even if they only implemented OS spellcheck compatibility on MacOS and Windows and just used the existing custom spellcheck on other OSes, that'd still be a huge improvement and they'd only have to do the work for two OSes rather than every OS that Firefox supports.
