What does that matter, if the comment is good? Nothing is inherently bad about those comments, just like nothing is inherently good about others.
Rather than a blue tick in the comment thread, it might be useful to have something like that inside their user profile. For example, animats has "John Nagle" in his "about" field. Having the information available but not initially visible might be valuable to help support claims like "As one of the early workers on network congestion" without coloring the interpretation of statements outside of his area of expertise (basically, avoiding attaching an "argument to authority" fallacy to every celebrity-posted comment).
edit: Bah, just saw your later comment where you suggested a similar mechanism. Sorry.