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I remember a story about a big @MastodonProject@twitter.com instance not willing to communicate with another instance. Do you remember what the instances were and where I could read about it?
@ploum
Toot Café has a list of blocked instances: https://github.com/tootcafe/blocked-instances. But I guess this is not the "incident" your are talking about since it seems to be like this for months.