Bad Manners and Brimstone

If they are looking at the post on their phone's FB app, it will bring up some choices for people to tap to reply to a sale post, rather than having the person type it all out themselves. One of those options is Interested. Many people tap that by accident when they are really just trying to scroll on the screen. Just reply asking if they have any questions, if the hit Interested by accident, they'll ignore you. Don't stress about it.

I did that exact thing by accident!

I wanted to send a message and when I clicked "send message" it just automatically sent them the single word "Interested"

I did follow it up with a message but it was very jarring to have it do that without me intending it.

So, it's not a thing that people are intending to do.  It's something that FB seems to do on it's own.