"""On the topic of the 2 of 10 rule, if it's to prevent one person dominating a thread, shouldn't the rule be "no more than 2 of last 10 should be by the same person in the same thread" (so 3 posts by the same person would be fine as long as they are in 3 different threads)?"""
I came here to say that. The means seem like overkill for the stated ends.
There is no rule against commenting more than 3 times in a thread. Sorry if anyone has gotten this impression.
However, among the 10 "Recent Comments" visible in the sidebar at right, usually no more than 2, rarely 3, and never 4, should be yours. This is meant to ensure no one person dominates a thread; it gives others a chance to respond to others' responses. One-line comments that quickly correct an error may be common-sensically excepted from this rule.
You need not refrain from commenting, just wait a bit.