Dave Troy 
Another design consideration re: Mastodon is that it works well for ephemeral asynchronous communications, but for many reasons should not be counted on as an archival resource. Media attachments are periodically purged and may not be available after a week, or a month, etc. While some servers may try to preserve content forever, this may be costly and unsustainable. Creators, researchers should treat this as an ephemeral resource and make provisions for self-archiving anything important.
I know Internet Archive just setup a Mastodon server and may have ambitions in this regard, and you can probably use it now to archive specific posts. Anyway I’m sure this will become of increasing importance as people start to post more original work here; that said, posting stuff to a separate resource you control is best practice.
Mike | Raymond Tec@davetroy Just so you, and others who may read this are aware: A few hours after you posted this, Jason Scott of the Internet Archive (@textfiles) specifically stated that they would not be doing this.
Apologies if you have already seen and addressed that.