Couldn't agree more. Twitter seems to be making policy in crisis-response mode, which is understandable but risky. A string of policy updates started in March with "broadening our definition of harm" (i.e., removable tweets) to include COVID-19 misinfo https://blog.twitter.com/en_us/topics/company/2020/An-update-on-our-continuity-strategy-during-COVID-19.html
The risks of ad hoc approach are 1) no coherent policy around what gets fact-checked; right now that seems to be only misinfo about either a) COVID or b) "civic processes," i.e. elections (that's how Trump's tweets on mail-in vote fraud qualified) https://help.twitter.com/en/rules-and-policies/election-integrity-policy
Last thought: It's hard to agree with @Wired's take that full-time fact-checkers like @PolitiFact "are often just as full of shit as the politicians they’re debunking." True, it's not hard to find examples of fact-checks that fall short, but that's no reason to abandon the effort
Full-time groups have what the in-house team at Twitter lacks: transparent methodologies with rules around who & how to fact-check. They list all sources, publish corrections, and adhere to a public Code of Principles with 75+ signatories around the globe https://ifcncodeofprinciples.poynter.org/signatories 
It's far from perfect (e.g. the @factchecknet principles just underwent a major overhaul) but it IS a good-faith effort to build fact-checking into an institution with norms & standards fact-checkers can be judged by. That's a huge asset for tech & media firms facing "infodemic"
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