Same account different servers would mimic discord. So you have one app, but the communities or ‘discord server’ can be their own instance. If it’s mimicking discord it will keep all the message boards private to users like discord, but it could still benefit from Lemmy/Mastodon integration. Many communities have a discord and a sub Reddit having the same account on both may be valuable to some people.
I don’t know the state of voice and video calls in the fediverse, it seems to be the main benefit of discord. Otherwise discord is just a terrible closed version of forums/subreddit/communities.