Theoretically, SoruceCred could support Twitter. We discuss this internally from time to time actually, and may do it one day.
tldr; it could be really powerful, but there are reservations around what behavior it could incentivize, and it’s not currently a priority. Part of this is just dev bandwidth. You’d need to create a Twitter plugin for SourceCred, which would involve knowledge of the algorithm and devs to build and maintain it. Also, SourceCred is currently focused on building a new plugin called the Creditor, which could serve similar needs. It allows you to input arbitrary contributions into the graph. This would allow someone to, for instance, submit a list of high-impact Tweets they’d made as a contribution. If the contribution is accepted, Cred would flow to those Tweets and its author.
As for incentives, if the payouts are high enough, you will likely be spammed/gamed. Point in case, 1Hive was running SourceCred on its Discord, including its #memes channel (link). Which is kind of a meme-focused social media feed. When their token ($HNY) mooned, the fixed amount of HNY they were distributing per week via SourceCred went from being worth ~$2k to ~$60k. People were making thousands just making memes. Pretty quickly, their meme channel exploded. Lots of brilliant memes at first. Then more spammy, low-effort memes…Eventually, people started gaming it with upvoting rings, which ruined the experience for many honest actors, and 1Hive had to set the #memes channel to mint 0 Cred. Gaming stopped almost immediately.
Another “cautionary tale” is the r/CryptoCurrency and r/ethtrader subreddits, which are distributing tokens based on karma (also a reputation system). Don’t get me wrong, I love these experiments, and I think they’re generally going well. But both subs also appear to have a “meme problem”. Many (if not most) in these communities think memes are over rewarded, but appear to have a problem reining them in. See r/ethtrader’s most recent governance poll related to memes and Twitter posts 
So, if Maker wanted to go this route, it will likely need additional technical and governance bandwidth, both of which are scarce due to other priorities.
On a personal note, I have enjoyed memes and comedy surfaced recently by @Uncle. Even though it’s a bit edgy at times, the community seems to have generally embraced it, and it’s the first contributor I’m aware of in a community using SourceCred that is making money just from art. This seems like an interesting experiment for the forum
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