@nhinkle: No, I don't think I should open and answer that question. It is not the question I had. How to turn off spell-check is well-documented, both in the browser help and on the web. The problem was that I did not know that the browser was spell-checking, not that I couldn't figure out how to disable that.

See my updated post and replies to your comments.

@nhinkle: Problem solved -- see above. Why on Earth dirs was autocorrected to dirs. I have no idea.

@nhinkle: I've tried to clarify the recipe, above. Yes, I thought it might be a browser thing. I tried googling for that, as well, with no luck. Perhaps someone else with IE11 can reproduce the problem, at least. FWIW, I haven't seen this problem in other edit fields (other web sites). Perhaps it has to do with the particular edit field implementation. I also see red squiggly spelling-mistake underlining and even automatic spelling "correction". That too I have not seen on other sites (but I don't edit on many sites).