Can anomaly combat sites have long chain escalations like the unrated signatures? Or are they limited to one escalation? For example, according to EveUni Drone Gathering - EVE University Wiki Drone Gathering can escalate into the Rogue Drone Asteroid Infestation, which is a bit odd to me because I think the latter is easier. Can this go on a chain just like the Moving day Chain?
Yes, combat anomalies can have long escalation chains, but you have to be very, very lucky to get to the last stage.
However, some chains can already have some nice things you can collect, but it hugely depends on the loot fairy.
In all my EVE time, I have never had the escalation go through to the last stage, they always ended early - which can be some odd 20 or more jumps away.
no, combat anomalies only escalate to DED escalations, which are 1-stage escalation.
unrated combat signatures can escalate to multi-stage expeditions.