Well we certainly consider it an important aspect! But also, as said, we were standardizing the existing set of federation functionality currently implemented in the federated social web.
But the Social Web Incubator Community Group has made anti-spam/anti-abuse stuff part of our mission, but that's hard stuff. ActivityPub does include federated blocklist support, but I think it's not enough. I've written about possible directions though: https://dustycloud.org/blog/possible-distributed-anti-abuse/
https://indieweb.org/Vouch (for Webmention, which is a much simpler spec, already a W3C Recommendation, and deserves more hype)
Vouch is a pretty clever scheme — as the sender, you include a link to someone who linked to you, who the receiver also linked to. So your server can detect, essentially, "randos" — unknown sites that might be spam, harassment, or good replies from someone who found your site accidentally.
I haven't yet implemented Vouch in my server software https://github.com/myfreeweb/sweetroll but my idea is to eventually have a settings switch that determines what to do with mentions from randos — reject, require pre-moderation or accept. Depending on your situation you'll be able to change it — e.g. set it to pre-moderation when some spam appears, or set to reject when a harassment campaign attacks you.
I think you have your priorities a bit mixed up. I would like an alternative to FB twitter. I can tolerate rest of the stuff until that minimum goal is achieved. Nor do I care that much about spam.
I have little hope that a spec not designed to reduce/stop harassment up front can have it bolted on later successfully.