I always assumed the "interesting!" markers were actual markers. A kind of tag for the system to annotate its context.

Probably does function like that in terms of highlighting context, in this case probably to the system's benefit.

But in general exclamations of "interesting!" seems like the stereotypical AI default towards being effusive, and we've all seen the chat logs where AI trained to write that way responding with "interesting", "great insight!" towards a user's increasingly dubious inputs is an antipattern...