I've been studying this verse of late and noticed the only other occasion Christ made a similar remark emphasizing the timing was when He informed Peter that he'd deny Him thrice by cockcrow:
"Jesus said unto him, Verily I say unto thee, That this night, before the cock crow, thou shalt deny me thrice." Matthew 26:34
"And Jesus saith unto him, Verily I say unto thee, That this day, even in this night, before the cock crow twice, thou shalt deny me thrice." Mark 14:30
So I wonder if you think Luke 23:43 should have the comma after "today" emphasizing the timing of his declaration not the timing of the thief's translation into paradise then shouldn't these verses likewise be translated similarly for the sake of consistency ie "I tell you tonight, you'll deny me thrice by the time the cock crows" rather than "I tell you, tonight you'll deny me thrice by the time the cock crows."
At the same time I should say I personally don't believe that we remain conscious after death as I believe it is akin to sleep as Paul refers to it in his letters (1 Corinthians 11:30; 15:51), but this verse has made me wonder if maybe what Christ meant was that the thief would rest in Him upon his death like all who die in Christ are assured of salvation (1 Corinthians 15:22; 1 Thessalonians 4:14).