I don't think it's a percentage of all comments. I think it's either the percent of articles (topics) posted to the site that are about Claude Code, or maybe a percentage of topics where at least one person mentioned Claude Code in the comments.

The latter seems easier to achieve. To borrow from another internet rule of thumb: "As an online discussion grows longer, the probability of someone mentioning Claude approaches one."

Well now it's 5.00001%.