What is strange about Discord is this great discrepancy between the ones that love it and the ones that hate it. If I were to guess on the reason of why that might be it would be that Discord is probably really good for the people that are constantly on it, and don't really miss any communication going in. These people have probably been there for some time so they don't feel the problem of not knowing where the past…
The first two are easily indexed by google, so that's one advantage. Twitter has a site-wide search. Discord doesn't (yet?) have such a thing, but I think the focus being private communities might keep that from happening... unless they get bought out and some MBA says "how can we better get clicks?"