I’m not happy to have software falsify my actions and I in no way consent to it doing so.
There is no falsification if implemented correctly. Every comment and post that you submit is an activity. All that the "community migration" should be doing is to take these activities and re-Announce
them, so it should look like a repost on Lemmy.
If the migration feature however takes the content from the imported community and creates new activities out of the comments, then yes, it will be shady.
Just to clarify: what would you say if someone followed your Lemmy account from mastodon and Boosted (Retweeted) all of your posts and comments?