I’d recommended you look into it, and potentially get another modem. If all my requests started taking another 30ms, I’d consider my network degraded.
This effectively means that even if your share of the total upstream link of a network "collision domain" (shared coaxial medium really) is low (i.e you're using less than 1/n and accordingly should not be experiencing queueing in the modem), you might be seeing latency spikes due to having to compete and wait for transmission timeslots.
My local DOCSIS link is experiencing anything between 0 and 60 milliseconds of latency which I suspect is mostly due to this (since it's inversely correlated to upstream bandwith).
I'd be interested in hearing counterexamples, but I imagine that people with good experiences are on DSL or Fiber.
That's not buffer bloat (but might nevertheless be something that happens on DOCSIS modems, although I haven't heard of buffering several packets before contending for an upstream send grant).
Buffer bloat, while also rampant especially in shitty CPE like most DOCSIS modem/router combinations, would only occur when your upstream is saturated.
Supposedly though, on DOCSIS, the upstream access contention algorithm used can sometimes add the latency you describe, adding latency even for single packets.
I realize that ping is a very poor benchmark as most routers do not handle ping in their fast path, but it's not adding 40ms of latency. So I suspect my modem.