I do not want you to delete comments to "shape the conversation". I want you to delete comments that are inappropriate for a public forum because they are offensive to reasonable readers, and thus are not part of a civilized conversation. I am also good with you deleting comments that are wildly off-topic, and thus do not contribute to the conversation at all. Setting a fairly high bar in both of these areas is OK, but I think blatant and gratuitous sexism, or a rant about the health care system attached to an article on an OS release, must clear that bar. I do not believe that there is a "slippery slope" here; if that is what you are concerned about, write a couple of paragraphs of explicit and detailed editorial policy on comments (such as many print periodicals have) and set it in stone.
Honestly, if I had posted either of the examples under discussion, I would both expect and hope that they would be deleted. You would be doing me a favor by helping to protect my reputation, and yourself a favor by helping to protect the reputation of LWN.
IMHO (having been involved with open source since before the beginning, and in my capacity as a college CS professor who deals with open source newbies on a regular basis) the "Wild West" nature of open source conversations is not helping us. I think it is a big part of what drives away women, people of under-represented ethnicities, older adults, and frankly a lot of really deep thinkers with a lot to contribute to our work. I would like to think of LWN as, among other things, a haven for those people. The comments should be an accompaniment to the measured and thoughtful LWN articles; failing that, they should at least not be an embarrassment and a source of discomfort and dismay.