Twitter will take a big hit from this.. given the current situation, will reddit take a big hit as well? it's definitely an interesting time where both blue bird and reddit users are looking for alternatives. Meta has a good track record of running social app, this can be a really successful product with the launch timing if the app fulfil the mass requirements from both sides
Reddit will continue to take several hits from their own weird decisions, I don't see how Threads will have much of an impact there. Not unless they start repurposing Facebook Groups features to encourage that same sort of community aspect to topics.
