First let me deal with the commerce-clause side issue. I don’t know what you’re talking about. You treated the clause as a limitation on federal power; I pointed out that it is, on its own terms, clearly a limited grant of federal power. Surely you can see the difference. That is to say: If there were no commerce clause, there would be less legitimate scope for federal power, not more.
Back to the main discussion. Your argument that the filibuster of judges is unconstitutional, as it has developed, rests on three points. 1) The Constitution sets out a limited number of cases in which supermajorities are required, therefore making a procedural rule that creates a de facto supermajority requirement suspect. 2) Judicial nomination is an executive power, and the advice and consent clause occurs in the section of the Constitution dealing with the executive; so in this case we do not have a purely internal Senate rule. 3) The Senate has traditionally not filibustered judges.
If any of these arguments were sufficient to make the filibuster unconstitutional, the others would be superfluous. But really none of these arguments work separately, and they don’t work together.
On point 1: Would you really argue that the Senate couldn’t establish a rule that makes it harder to raise taxes? Over the last decade and a half, budget rules have created de facto supermajority requirements for tax increases. Do you really want to argue that they’re unconstitutional? If we are to infer that all supermajority requirements that are not authorized by the Constitution are therefore prohibited by it, we would have to reach these absurd conclusions. So argument 1 doesn’t work.
Point 2: So are we then to retreat to the more limited position that the Senate can’t adopt a procedural rule that sets up a de facto supermajority requirement when it touches on a presidential power? That is an awfully specific, and convenient, rule to infer from, well, nothing. (Is there, incidentally, a de facto supermajority requirement at all in the sense required by your argument? On your argument and mine, 51 senators could change the rules if they felt like it. If they retain the ability to confirm nominees they approve, what remains of your argument?)
Point 3: Your latest post claims that for 200 years, most senators understood the filibustering of judges to be unconstitutional. You haven’t come close to proving that. All you’ve shown is that they have not usually filibustered judges–they may very well have thought they had a theoretical right to do so, but declined to exercise it. Or maybe they had no view one way or the other.