I'll give you a 'for instance'. Tonight, I am posting on this site. Does that mean there is some deep, mysterious reason I used the word tonight? I used a comma too.
Your example is not really equivalent to the manner in which the idiom was modified in Luke 23:43.
A better example would be something similar to the following:
?Dude I?m telling you tonight I am posting on this site.?
If you did not normally use commas and you constantly used the phrase ?Dude I?m telling you?, most people would recognize ?Dude I?m telling you? as an idiom and assume that a comma would normally follow the idiom. Unless there was some significant reason, the comma would always follow the idiom. So, the above phrase would read as follows:
?Dude I?m telling you, tonight I am posting on this site.?
It is not at all surprising that Jesus or the writer of Luke would have believed in a literal Hell. This is not to say that they believed exactly what many people today believe about Hell, but it is obvious that they were influenced by teachings that had become popular prior to the first century.