In other words, perhaps CBS C699T +/+ and various other problem SNP remain relatively harmless, except in certain contexts.
That doesn't mean that something isn't causing CBS to dramatically malfunction, but it does exclude CBS C699T from playing that role. If there is something interfering with CBS in such a manner, it would have to be entirely external, and would have nothing to do with specific SNPs on the gene.
Also, it's generally claimed by Yasko and her followers that CBS C699T +/- and A360A +/- and +/+ also cause problems, not just C699T +/+. If well over 50% of the world's population had this supposed vulnerability to exploit, it would be massive and it would be extremely noticeable.
And for the 31 ME patients from this forum who I have 23andMe data for, 2 are +/+ for C699T and 12 are +/-. For their ethnically matched controls, 5 are +/+ and 17 are +/-. If CBS is causing problems, it's very unlikely it's contributing to ME, and is certainly not looking to be more prevalent in ME.
I also still have not seen anyone attempt to explain how synonymous alleles in exons could ever cause problems, such as for CBS A360A and CBS N212N.