I just created an account with Obsidian and moved our journal with over 9000 entries from MacJournal onto Obsidian. I’m happy with the ability to continue the journal on what is presumably will be a more reliable platform, but do people have recommendations for other features of Obsidian that are useful in journaling?
Doesn’t necessarily have to be a plugin but is essential to journaling:
Have a solid backup system in place.
Folks who move from online to local file apps don’t always know that… until they find out 
. As part of my backup system, I use the Local Backup plugin and have found it reliable and easy to use.
If you mean plugins, the best advice is to not use plugins until you find some type of pain point or rough edge you’d like changed, or a feature you really want, then look for a plugin that fixes that. Going overboard with plugins, especially early on, is a quick way to overwhelm yourself.
If you mean actual built-in features, Templates and Daily Notes are both exceptional. With a little bit of creative tweaking of the dates, you can turn the Daily Notes into Weekly or similar, as well, if you don’t want a daily note.
If you have a bit of passing familiarity with CSS, Snippets let you do some pretty nice customization for different aspects of your notes, both as a whole and with the inline text.
I second the recommendation of the Templates and Daily Notes core plugins. My entries follow a certain format, and templates save me from writing the date & such out by hand. And Daily Notes saves work setting up each new file (I have mine set to make weekly notes instead of daily, which I use as an overview for various themed journals/logs.)