X published its ranking code. An open link scores 0.2 there. A reply or a quote scores 5.0.
Links are not punished. The code has a penalty for them and it ships turned off. They just carry very little weight. Your opening post is the only part of a thread that is not already a reply, and a link is the lowest-scoring thing you can ask a reader to do with it.
So when you put an external link in an X opening post, a suggested reply now appears underneath it, already written. Accept it and the link moves down into the reply, with a line above introducing what is at the other end. Keep it in the post and the suggestion goes away for that link.
You are always the one who applies it. The reply is there to read first, and the toast has an undo if you change your mind.
A post that is only a link
A bare link has nothing left once the link moves, so we write the opening post as well. Both halves appear labelled with where they land, and you approve them together.
Type your own words while it is still thinking and yours win. The only reason we wrote a post was that there was nothing there.
If the link is yours
We compare the link against your workspace website, name, and account handle. On your own site the copy says "we added" rather than "a new tool from". Anywhere else it stays neutral, and it will not claim someone else's writing as yours.
Fill in your website under workspace settings and this gets a lot more reliable.
Where it appears
X only, on the opening post. Not on replies, not when the post has media attached, and not when the link is a quoted X post. A quote scores 5.0 as well, so those are left alone.