simply turning off "spell check" = no good. way to easy to open up another tab / window in the browser (does not even have to be another moodle page). and "BAM" instant feedback if good or bad word spelling
never have used it. but have seen it repeated enough.
allowing teachers to lock down different things. as needed, when needed.
instead of a "SINGLE text box"
what about individual text boxes "s" "p" "e" "l" "l" "i" "n" "g"
so student needs to either click "tab key" or "enter key" to move to the next box. each box can only have a single character in it.
i would imagine this might prevent some auto spelling.
but then there is a second issue. "auto fill" in many browsers.
example goto some shopping / eCommerce website. fill out your email address, street address, and you get a pop-up allowing you to click it, and have most if not everything else filled in (country, state, zip code, rest of street addresses, etc...)
a flash applet more likely work better and prevent "auto filling" and disable "auto correct spelling" across all browsers, and devices.
i want to say there is a setting "some place in moodle site admin menu" that restrains students to a "single" session. no other webpages open at one time on moodle website. but that is at site level. and not able to turn on/off as needed for courses for a specific amount of time.
i can only think of use of spellcheck='false' as a way to initial prevent student getting "auto corrected spelling", and if they did open up a new tab / new window in browser. they would have to do extra work to obtain it. and still required to type in correct spelling into the "answer/text box" possibly copy / paste might work as well, which then you do not even get "eye / hand memory" of typing in answer.