Gregory's Server@tokyo_0 So you mean if someone with hundreds / thousands of messages migrate, it will respam them on the local / global feed ? That would be an instant ban from me, I think, because that would be, well, spam… We're a small instance, the local feed still has meaning, this would pollute it by reposting content that is not tied to a specific date and time.
@RGrunblatt It won't do that unless they specifically override the default settings and all of their messages are set to "public" visibility.
By default the tool reposts users' public posts as "unlisted", to avoid the problem you describe.
I'll add that to the administrators' information on the website to make it clearer — thank you for asking about it.