There was a few (I last remembered at least 5) comments on the question I posted, suddenly disappeared and only left with mine. At least 2 user posted the comments. I seriously doubt they deleted all of it.
Moderators regularly clear off-topic/not contrustive/rude/out dated comments.
Your comments were probably left because they related to adding further detail to the question, ideally those comments are edited into the question as further detail and they are then deleted also. Lets focus on keeping the house tidy. Someone visiting the site will have better results with a clean question and answers, comments are great to get the best answers possible and occasionally there are a few of discussion that are worth keeping but they should be generally included in the related post.