Concepts in code blocks are not clickable in the PDF. Perhaps you've found a bug for https://github.com/Eelis/cxxdraft-htmlgen? Indeed, it seems concepts are not linked to their definition in \tcodes.

Yep, since I can only make a pdf document, I have no way of knowing whether the commit successfully makes the concept clickable, although it seems to be.
Note that currently at [common.iter.nav], it is not clickable.

Yes, but you should report that at the repository linked above, which is concerned with eel.is's output.

\exposconceptnc is for avoiding automatic italics correction in certain corner cases. Unless the argument is bad formatting by LaTeX, this will stay as-is. Other than that, this is not an inbox for bug reports about the rendering on https://eel.is/c++draft/ .