I got 3 correct matches out of 20, and I've had about 6 accounts total (using one at a time), with at least a fair number of comments in each. I guess that means that my word choices are more outliers than yours or there is just more to match. So it's not really good enough to reliably identify alt accounts, but it is quite suggestive.
I think if you rule out insanely common words, it might get scary accurate.
Actually, the way that these things work is usually by focusing exclusively on the usage patterns of very common (top 500) words. You get better results by ignoring content words in favor of the linking words.
Interesting, I think it also doesn't help that outside of a throw away on a blue moon, I don't really use alts...