Reddit mentions of The Living Constitution (Inalienable Rights)

I'd recommend reading the original op-ed.

Then in turn, look at the book written by the author Posner cited, David Strauss, called The Living Consitution (Inalienable Rights).

Posner is NOT saying ignore the constitution. He is, however, against head in the sand originalism.

Your question here and your broader question is really hard to answer succinctly. There are whole classes taught on this. Here are a few points that may be helpful/resolve your curiosity, though.

First, another way of referring to following precedent is the principle of "stare decisis." That may be helpful in running google searches.

Chief Justice Rehnquist, in refusing to overturn Miranda (which, as you may guess, established Miranda rights) indicated that stare decisis is very important, and there must be a "special justification" to depart from precedent (but less so in the context of constitutional decisions): "While stare decisis is not an inexorable command, particularly when we are interpreting the Constitution, even in constitutional cases, the doctrine carries such persuasive force that we have always required a departure from precedent to be supported by some ‘special justification.'"

But not all justices, lawyers, and scholars agree. Most notably, Justice Thomas does not care much for stare decisis (in the context of both constitutional and statutory decisions). According to Justice Thomas, a court's job is to enforce the Constitution (or statute) itself, not any court's interpretations of those laws, so precedent carries very little weight: "When faced with a demonstrably erroneous precedent, my rule is simple: We should not follow it. This view of stare decisis follows directly from the Constitution’s supremacy over other sources of law—including our own precedents. . . . In sum, my view of stare decisis requires adherence to decisions made by the People—that is, to the original understanding of the relevant legal text—which may not align with decisions made by the Court. Thus, no 'special justification' is needed for a federal court to depart from its own, demonstrably erroneous precedent."

Ultimately, different justices may have their own views on how it should work--but, really, the bottom line is that nothing besides their own restraint prevents the justices from overturning precedent.

As to how exactly these reinterpretations of the constitution occur--as you note, the text of the Constitution itself hasn't actually changed--this is the subject of much scholarship and debate. If you're interested in learning more about it, I would research the idea of "living constitutionalism," and perhaps read this article/get this book (both by David Strauss, one of the most prominent proponents of the idea that our constitution is a "living document").

This might be a helpful resource if you want more information.