Currently there is a visible jump when the button loads in the middle of a log row or a history row. The addition of the button causes the text around it to move.
We can prevent this jump by adding some extra padding after IP address links before the JS loads, then removing this padding once the JS loads.
Caveat: IP address links are recognised by the presence of the class mw-anonuserlink. However, this class is also added for IP range links, which do not get a popup button. So if we make this change, we will instead get a jump for rows with IP range links. They will initially have padding, then the padding will go away when the JS loads (but no button will be added).
To distinguish the IP address and IP range links we'd have to manipulate the HTML using PHP, which is fiddly and I think not worth it.
@Prtksxna If we do this task, we will no longer have a jump on IP address rows, but we will have jumps on IP range rows. If we don't do this task, it'll be the other way round. What do you think we should do?