If an unknown new tag is deleted then it was a typo.
	The next already-known tag is its correction.

"learnReplacement"  =>  {newReplaceTags}

addTag
	if new tag
		learnReplacement

removeTag
	if matches learnReplacement
		remove learnReplacement

done
	if learnReplacement is still in list
		add it to learned typos
