I recently mentioned that Gmail's spell check bug, in which apostrophes in words are interpreted by the spell check as whitespace, and thus treats the parts to either side of them as individual words, was fixed. I appear to have been mistaken. It seems the bug only appears in certain situations. I'm not sure of the specifics, but here's my best guess based on playing with it for a while...

First, let me explain an apparent feature in the spell check system. When you reply to a message, Gmail will automatically ignore any misspellings from the original message when you go to spell check your reply. This is useful, because you should never alter a quote from the original message, so why should Gmail bother telling you that there are errors in there? Any misspellings in the original message that you repeat in your reply are also ignored. In some cases this can be useful, and in some cases it could be a bit of problem. But the way I see it, if the first person spelled it wrong, who cares if you do, too?

Now, here's what I noticed: When I checked the spelling of a reply containing simply doesn't by itself or in a short sentence (without quoting the original message), it didn't mark it as incorrect. However, if I included an unrecognized word from the original message (or if I quoted the message), the bug would occur. For example, I was replying to a message that mentioned the word blog, which currently, ironically, isn't in Gmail's dictionary. The bug occurred only when I included blog in the reply.