All of the spelling checkers that I have encountered have a basic flaw, and that is that if you don’t recognize the correctly spelled word from a list of words you might choose the wrong word. Typically they have a drop down menu of various words which the program thinks might be the word you intended to spell correctly. The WordPress spelling checker works this way, and it is acceptably good so far as it goes, but what it lacks, and all the others lack is a definition of the various words it presents. Even a single word definition to the right of each suggested word would be a great help.
An even better solution to this problem would be to have several words appearing to the side of the drop down list which are synonyms of the suggested words and which are themselves click-able. This word checking quality could be applied to all of the words in the document, not just the misspelled ones. The user of the program could by highlighting, or simply pointing at a given word, and clicking it, or highlighting a phrase, choose a more appropriate word, or phrase, and insert that into his document.
A simulation of the word “presents” is misspelled as “pretents” and it would show up in a typical spell-checker drop-down list about like this:
But in my new and improved spell-checker’s drop-down list it would be more like this:
—pretends, imaginary, invented, false, sham, fictitious
—presents, now, nowadays, gift, give, bring forward, demonstrate,
—pretests, preliminary test, practice, practice test,
—prevents, forbid, preclude, forestall, keep,
—portents, omen, prognostication, presage, prodigy,
Any of the words on the more complete list could be clicked, and it would enter the document in place of the previously highlighted word. I don’t think it would be to difficult to program these additional functions into the existing WordPress spelling checker as it is just adding a list of click-able words to an already existing list of click-able words.