Impressions: I didn't do any actual statistical tests, just massaged the data a lot.

For almost every subject it was possible to complain about, the people who complained about it were a diverse group. Particularly, I noticed that they were diverse in terms of how much of LW they'd read. On the other hand, people who marked an unusual number of complaints were more likely than usual to never have commented.

Comparing people who have both read and commended on LW to everyone else, the full users had more complaints on average (meaning that the prolific complainers were small minority among non-commenters). Full users were less likely to complain (proportional to amount of complaining) about focus on AI or criticism of science, and more likely to complain about jargon. On the community side, they were more likely to care about overly high standards and website design, and also somewhat more likely to care about in-person interaction.

Complaints are not correlated very well. For example, the correlation between full users who complained about software and full users who complained about high standards was very low (though I think significantly positive). There didn't seem to be any large population of average complainers, just a bunch of people with different opinions.