The definition is not very important, but I don't think you count as a lurker. Lurking is more like total non-participation, not occasionally participating. You're also probably above the median for karma on Less Wrong.
Anyways, all are welcome in this thread.
Some research says that lurkers make up over 90% of online groups. I suspect that Less Wrong has an even higher percentage of lurkers than other online communities.
Please post a comment in this thread saying "Hi." You can say more if you want, but just posting "Hi" is good for a guaranteed free point of karma.
Also see the introduction thread.