Block the user. It should be just one bot doing it in the lemmit.online instance.
To do so just, from your instance website, click on his name and search for the block function.
EDIT: For future reference you can automagically hide all (properly flagged) bots’ posts toggling the “Show Bots” in your profile, but you will lose the useful ones too and the one not flagged will still appear.
Block the user. It should be just one bot doing it in the lemmit.online instance.
To do so just, from your instance website, click on his name and search for the block function.
EDIT: For future reference you can automagically hide all (properly flagged) bots’ posts toggling the “Show Bots” in your profile, but you will lose the useful ones too and the one not flagged will still appear.