I don't know dakimov and what his history may be (maybe it's even a language issue or that he simply doesn't "speak HN" yet - I also sometimes find myself out of touch with the culture on this site like he seems to be), but I can vouch for what he's saying. I find it difficult to read discussions about C on HN. A lot of the discussion is as if to read a bunch of kids who seemingly just learned javascript or ruby yesterday, then they go way out of their element talking about C. An experienced and competent C programmer would not be surprised by anything in these slides, except perhaps the slide about the novel use of "static", because it's an obscure C99 feature that nobody really uses (in the same way that most people would also not recognize that, for example, C99 specifies compiler support for complex numbers).
I am an experienced and self-proclaimed competent C programmer and I was surprised enough by the "static" feature which I already love -- that I immediately upvoted this, and I'm going to spread this information after testing that it is actually usable with the common tools we use.
Sure, the other stuff was either UB or less interesting to experienced C programmers, but I'm not sure why that should be a problem. If you already know all of these, then you're not the intended audience. You can comment from a more experienced position, or just move along.
Bragging about knowing all of those and even worse - claiming they are just silly UB, all in a condescending tone as dakimov did, is a very stupid thing to do.