This is a very good question, and unfortunately we aren’t able to address it officially. We asked a local charr for their input, but while our colleague is expected to make a near-total recovery, office safety policies preclude us from risking it ever again.
In the interest of your family’s well-being, we’ll turn this question over to the community at large, and then run away quickly! Do charr purr? /ᐠ｡ꞈ｡ᐟ\
If charr are anything like actual cats, then it’s likely that all can, but not all can purr continuously. Small cats can purr on the inhale and exhale, producing that rumble we all love. Big cats can only purr on the exhale, so theirs sounds kind of like a sputtering engine (or really bad snoring) instead of a nice rumble. Interestingly, it’s the big cats that can roar that have the choppy purrs, and this has to do with the structure of their hyoid bone: cats that can rumble-purr can’t roar, and vice versa. I’d imagine that any charr that can give that oh-so-intimidating roar is probably hiding their stuttering purr.
Just go very close to a sleeping charr. You’ll hear your answer.
