Honest question, where does one use a spellchecker in the browser ?
This is one of the features I appreciate a lot. I am not a native speaker of the English language, and I sometimes mix British English and USA English, and the spell-checker helps me to write consistently better messages.
I myself (not a native speaker) am very pedantic about setting all my software to enUS and turn all spell checking off. (I can't even stand the linter underline in VS for example, it ruins my focus, especially when it underlines as I type and then lags before disappearing at the end of the word)
The only place where I use spellcheck is e-mail at work to avoid typos. Over the years I've learned to proofread my messages before sending them and touch typing helps a ton as well.