Huh neat!
I spent the first little while thinking that they were indeed very rare, only to realize that I had failed to actually turn on the hints (didn't hit save or something?). After that, they were showing up 100% of the combats I saw — not entirely rarely but pretty unobtrusive so not a big deal. Nice that it's written in-world style.
Experience so far, fighting hounds in the buried lab:
First time, I got a message "things might have gone differently if you'd rested up before the fight." I never saw this again, even if I started a fight at 2-3 HP. Maybe that message should show up more often if you ever start with < 10 HP or something?
After that, I got a couple dozen messages saying "defenses may not have kept up with your opponent's attacks". This could be misleading perhaps, because I was still getting it with decent Melee Defence here (all opponents were doing minimal 1-2 damage) Perhaps only show this message if an opponent got in a attack that did > 4 damage at once?
When my power is low and defense high, I couldn't do enough damage to take down the hound before he took me down. (Us both doing 1-2 damage per attack). Advice here to boost your attack power or try to make longer chains* if the fight lasts more than 5 rounds, or if you don't ever manage to do more than minimal damage?
(* or, this may or may not already work this way, but depending how spoilery you want to go, if an opponent is weak to a ranged damage and you are trying melee attacks, suggest a different damage type?)
I'll let you know if anything else comes up!