Search @communityname@instance.domain in Mastodon. It should come up with something. That said, the latest Lemmy version has a known bug that temporarily breaks this in some cases.
Nothing a quick patch can't change. Lemmy code is open source and can be edited by anyone running an instance. If it hasn't been implemented it's because it's not yet a priority with all the influx of new users stability is more important.
This is all fairly standard for fediverse software, but many people do not know this.
Lemmy is a bit better because it does not distribute images, but also worse regarding message deletion. While Mastodon servers delete content when they receive a delete request, Lemmy only hides it. The reasoning is that it's supposed to be able to help with moderation if admin and moderators can see what content was deleted, but I don't think it holds water. In the following months I will try to find a way to have Yiffit.net's server fully comply with deletion requests received by the author of some content, whether a local user or a remote one.
600 tweets a day is nothing. One could easily do that in an hour or so.
Not saying it's the healthiest thing to do, but it's very easy for regular twitter users to hit that limit very soon.
I would definitely be one of the "bite me" crowd.