Hey @avmccoy ,
Thanks for posting on the Instructure Community!
I recommend that you navigate to your canvas course's settings, and under the Course Details tab scroll all the way down. You should then see some options that you're able to check/uncheck. At the bottom, unless otherwise set-up by your institution, you should see one that says "Disable Comments on Announcements", you'll want to check that on.
From what you are explaining, it seems you're just checking it off on a single announcement, so I feel that having this enabled will save you a few headaches.
It is also possible that your canvas admin set it up in a way where comments are always enabled on announcements, and you don't have the ability to turn it off. It doesn't hurt to try either way, though.
I'll provide a picture below of where I'm referencing in the course settings to turn this setting on, if you require the additional help.