Responding to your 5/29 2:26 post: I didn’t see this post until I’d posted at 2:57. However, it turns out that I had done what you’d suggested anyway, so that my machine had no trace of Sublime or its repositories before I did a clean install using the official instructions for apt.
Responding to your 5/29 3:05 post: OK, mystery solved! I think we’re both right. Examining the contents of my file /etc/apt/sources.list.d/official-package-repositories.list, I find that the first two lines are:
deb http://packages.linuxmint.com rafaela main upstream import
deb http://extra.linuxmint.com rafaela main
The second line references 13 packages such as dropbox, google earth, virtualbox, (most of which I use) and, yes, sublime-text version 3103! See http://extra.linuxmint.com/list.php?release=Rafaela
So I’m thinking that apt is picking up sublime from there, regardless of anything else we do. Are the official package repositories in linuxmint.com a “rogue apt repository”?
Thanks so much for your persistence. I’ve learned a lot.
Final question: Is there a reasonable way for me to install Build 3176 without hacking my system? Would it be safe for me to do so? At this point, I’m also OK with leaving things as they are for now.