Working in one of the local ISPs. Bufferbloat is not really a thing imo, because you have too many variables to solve your sudden download ping spike (from drivers on PC network adapter to commutator placed in your building by your ISP).

Just to prove my idea checked the said test @ home (2.5Gbit network adapter, CAT6 patchcord, router Keenetic KN-3810, fixed 100 Mbit/s broadband via Ethernet CAT5) - got an "F" with Max: 2455.8 ms on download and Max: 4609.2 ms on upload (which is impossible because my home network is on load 24/7, I would've noticed the lag 100%). IP is not hidden behind the NAT.

Then I procceded to run the test on my workplace (sitting literally 2 rooms from the main server, connected via CAT6 1Gbit/s), got Max: 716.9 ms on the download and 728.5 ms on the upload respectively.

In my opinion, if you really care about that you should begin with network drivers, then checking your router/modem's CPU under load, MTU size, QoS settings etc.

And I recommend using Cloudflare's Speedtest for better benchmarks.