Well, it really depends on what your definition of a pension and a promise to pay money is and on whether that constitutional provision is to be read narrowly. If the US government collects money from people in the form of a tax and tells people that it is a trust fund for payments in their old age and then uses that money like it was a source of income, that is basically a government note, a bond, in exchange for payments in old age. Is that a pension? Yes. In my judgment. I have never heard any argument that I thought carried any weight otherwise. If any private entity had done this, with compulsory or voluntary pay-ins, it would certainly be a pension and a debt. The question is whether the US government can turn it’s back on 75 years of collecting money and making payments this way as a matter of constitutional law. As the Supreme Court has shown us over and over again, this is a matter of the political leanings of a majority of the members on the court. I hope the issue never arises in court, but it probably will.
I’m still not clear about who writes the congressional paychecks. I tried to Google it, but I haven’t found correct keywords. You would think think it would be easy to figure out if Congress has their own payroll office or if the Treasury department cuts the checks.