Seems the WT comma placement explination makes sense.
Some would remove the stop, and place it after "today", and read the words thus, "I say unto thee today"; as if Christ only signified the time when he said this, and not when the thief should be with him in paradise; which, besides it being senseless, and impertinent, and only contrived to serve an hypothesis, is not agreeably to Christ's usual way of speaking, and contrary to all copies and versions. Moreover, in one of Beza's exemplars it is read, "I say unto thee,
that today thou shalt be with me", &c. and so the Persic and Ethiopic versions seem to read, which destroys this silly criticism. And because this was a matter of great importance, and an instance of amazing grace, that so vile a sinner, one of the chief of sinners, should immediately enter into the kingdom of God, and enjoy uninterrupted, and everlasting communion with him and that it might not be a matter of doubt with him, or others, Christ, who is the "Amen", the faithful witness, and truth itself, prefaces it after this manner: "verily I say unto thee"; it is truth, it may be depended on. This instance of grace stands on record, not to cherish sloth, indolence, security and presumption, but to encourage faith and hope in sensible sinners, in their last moments, and prevent despair. The Papists pretend to know this man's name; they say his name was Disma; and reckon him as a martyr, and have put him in the catalogue of saints, and fixed him on the "twenty fifth" of March.