This post is so trivial as to be flagworthy. If the author's coworkers ask him about design decisions, invariants, or other minutiae regarding a piece of code,

This post is so trivial as to be flagworthy. If the author's coworkers ask him about design decisions, invariants, or other minutiae regarding a piece of code, does he explain it to them by writing more code? No? He uses natural language? Then perhaps there are times when an inline natural language comment is warranted. End of argument.