@tmalsburg Three reasons: (1) the local time on sigmoid is more interesting for me, (2) the server seems to be faster (I already experienced it on @AmsterdamNLP), and (3) I was warned that many smaller instances block or will block mastodon.social.
(I am also not so happy with these walls between mastodon instances, but am aware that others might have very different experiences on social media than I have and don't have strong opinions about their necessity).
@josipk I followed this recipe:
https://mastodon.social/@Gargron/103393780267601137
with the new account in a private tab, and the old account active in a regular Firefox tab. It took some time for almost all my followers to be migrated. I saved my follows to csv on the old account, and uploaded them manually on the new account.