I think a lot of people use the "self-documenting" excuse without knowing what "self-documenting" really is, and what it brings to the table. Self-documenting code is a good fit for a reasonably small and straight forward function. If you have a function called get_thingy() in the context of some sort of "thingy container" then you probably don't need to go out of your way to explain "This method gets a thingy from the thingy container."

This can even be expanded to more complex single-purpose functions that are not exposed directly to any external APIs. For instance, if you have a functioned called restart_thread() which first tries to stop a thread, then stats a new one then you might be safe.

However, as soon as you leave the realm of the obvious, comments are a must. Clearly in situations where you're trying something clever, like that Q_rsqrt function, missing comments will boggle all but the most specialized professionals.

Unfortunately people often forget about another important type of comments; those that explain what function this piece of code serves in the program. I've lost count of the number of "Context"s or "Interface"s or "get_data"s I've seen when trying to read someone's code. In those situations a single line like "This context links the rendering pipeline to the physics simulation" would go a very long way.

Instead when I see this sort of code it will either not have any comments at all, or it will be a dissertation that all the theoretical uses of the piece of code (Omitting what it's actually used for in the current context).