I have been looking at this for the last few days and have a possible decode. The underscore could be designating a missing letter. As Q has done in the past. So I started by looking for words that are scrambled within the main body of CASTLE ROCK. Being that this is in a context of part of a time line one word stands out. "CLOCK" which leaves " _ASTER". There are several words that you can make out of this using different letters for the underscore but ONE stood out to me using the letter "R".
"ARREST CLOCK"
I keep thinking about how amazing it would be if Castle Rock referenced Castle Rock Films and the Q team was putting a film together for the normies. Or confession tapes. Hope porn is a helluva drug.
Didn’t a certain no name also sport the boot before they died....
Yes. And he “died” without ever taking it off, too.