It happens because there are two words exist in the main dictionary: "com" and "mitt". And as I wrote here
in the "Checking behavior" part ReSpeller tries to split word into two parts and check each of ones separately. In some cases like yours ReSpeller skips wrong words, but so he recognizes better some words like "filename", "directorypath" etc which not splitted by camelHump. I met a lot of such identifiers in many projects.