Like the last cited posting actually mentions, it turns out that IgG4 antibody responses are common with chronic exposure to an allergen (like the various constituents of a vaccine or a bee sting) and usually don’t do or signify anything except for the fact of chronic exposure to something. Repeated COVID mRNA inoculations over a one or two year period qualify as chronic exposure.
This review (“Immunoglobulin G4: an odd antibody”) puts things into better context: https://instytut-mikroekologii.pl/wp-content/uploads/2017/12/Immunoglobulin-G4-an-odd-antibody.pdf.
I apologize for my over-excitement and consequent hastiness. Although the earlier data indicate the immune response to multiple vaccinations is indeed blunted and therefore afford little or no additional protection, the later IgG4 increase itself also has a more or less neutral effect on those multiply inoculated.