Kelon
Two principal problems are probably Big Money gaming the system and people not wanting to publicly disclose their views. In the worst case your scheme might end up serving age-old staples of propaganda: Falsely implying a consensus and the establishment of authority (of the most trusted users).
I'll keep a look out for how you try to deal with that in the future.
You use the term "propaganda" like it's something that can be determined objectively and algorithmically the way that spam can. That's very concerning to me, seeing as mega corps like Facebook and Google are also starting to implement questionable protections against what they consider to be propaganda. And similarly, they also group them together with other issues like terrorism, hate speech, etc. That's exactly why decentralized and uncensored forms of communication are so important right now.
How are you planning to determine what is propaganda? By your own perception? Will you refer to a team of "independent experts" as the arbiters of truth?