Hi @neil,
That sounds like exactly the steps I took as it happens, I think the only maybe different was that after the link got oneboxed in the body, I changed the title (as you mentioned) and then changed the body. It wasn’t until I had posted that I noticed the little link under the topic. At first I thought it was coming from the URL I had pasted into the body, so I tried removing it but it remained. It was about then I realised the clever title to link functionality which I hadn’t really read about in detail here before but had seen the odd topic mention it so assumed it was related.
Coming at it from a user (one clearly prone to mistakes!) my first thought was about how I would remove it. I tried changing the title again, just to “http://” to see if it would change it at all, but it didn’t, hence then deleting it and recreating it.
The body content is obviously easy to remove if you go wrong, as I did, it’s just the link, having a little hover with edit/remove would probably be what I would have expected once I realised what it was.
It’s not the end of the world, but again, as a user, I wasn’t familiar enough with this feature to appreciate the steps to produce it, or avoid it - I’ve also never used Reddit (as is probably clear from this post!) 