The spam goes both ways. Nostr's loose moderation was used (maybe still is) to spam over the bridge. That's the reason a lot of servers blocked them.
Well there are definitely servers that don't federate with Mostr or Momostr... But there are other servers that do, and posts don't show up... So I think there are other issues.
As for spam, yeah there's some, but there's good content too... I've been enjoying nostr:nprofile1qqsyk3sjx32e4xs5qj2rtcwapeyrj95yfn4d4h7kkhdgyjc409fmmespr9mhxue69uhhyetvv9ujumt0d4hhxarj9ecxjmnt9urzqpjr for instance
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Makes sense. I guess we had that coming.