So, I've concluded that these little bursts of packet loss are really just some failed equipment of the backhaul carrier, and that it isn't fixed yet is most simply explained by incompetence. I just discovered it affects other connections locally.
So I'm bringing my Tor relay back online, and throttling it up so that it now eats twice as much of their bandwidth \o/
(I thought it prudent to keep the relay offline until I understood what was really going on. Short bursts of packet loss like this, if someone was doing that deliberately with a set pattern, would have been an ideal way to watermark streams going in and out of the Tor network, to do some timing correlations. But I'm satisfied that's not what happened here.)
Stay vigilant!
Regards,