After reading the answers here , @musing , it sounds like a good idea to provide a quick search serverside like you get on customer service sites, based on keywords, providing "already posted" questions containing the same keywords and the question "did you mean ... blablabla ... " (you know what i mean, lol)
in order to prevent unpleasantry, i dont think its realistic to expect all and everyone to go deep-searching for eventualities before they post, from a friendly customer perspective its probably the way to go too unless one wants to push all responsibility to the client which in 2018 is not everywhere accepted anymore
you already have the search box, i doubt i will require oodles of extra code to implement something that can prevent a lot of hassle
wouldn't you agree ?