Edwin probably never had anyone to talk with in hell, right? Maybe the occasional other person popping up like Simon did but even then Edwin had to be quiet because of the spider demon.
So I like to imagine that during the first few years with Charles, Edwin would think stuff in his head but not say them out loud and then be all frustrated and confused when Charles was like 'mate, I have no idea what you're going on about.'
Maybe having problems with speaking too softly or in broken sentences half said out loud and half only in his head.
And that'd be one of those weird quirks of his that, years and years later when Charles finds Edwin in hell and is told very desperately to be quiet, finally clicks and Charles goes ohhhhhhhh. Oh no.














