@patricia
Thank you for this info ... I've been a confused about this cultural difference. I found an explainer and changed my defaults too.
my ref.
"There are also some conventions around these privacy settings that many instance administrators ask users to uphold. For example when writing a thread, the first post can be public, but subsequent ones should be set to unlisted as to avoid flooding the federated and local timeslines with several toots sent in rapid succession on the same subject. These timeslines are for discovery of new users, and to easily start conversations and should be kept mostly clean from conversational traffic. Consequently, replies to public toots should also be sent as unlisted or followers-only (if more private)."
@amytabb I just set my default to unlisted then making something public is an explicit action