I actually use the live preview feature, no idea how I never noticed this. I guess I stopped editing talk pages using the normal editor ;)

This is actually a bit awkward to fix, because in the hook which we're using to add the reply links, we don't know whether we're showing a normal page view or a preview. (Also – we don't have this for non-live preview either – now that I think of it, I have no idea how come we don't have the same problem there. This might be a separate bug that is accidentally cancelling out with our bug.)

It will probably be easier to fix after T267404: Add reply links to the parser cache, because we'll be able to access the parser options from our code then.

In T267860#6625221, @matmarex wrote:

I guess I stopped editing talk pages using the normal editor ;)

Sometimes I need to start new sections, which is not yet supported. Otherwise yeah, same here.

It will probably be easier to fix after T267404: Add reply links to the parser cache, because we'll be able to access the parser options from our code then.

Okay, no hurry. Should we add that as a parent task to this task to make this dependency “official”?

I can't reproduce this any more. Looks like it has been fixed by rEDTOda72fb15c21b: Only show reply links when body class in present (which also fixed T274311: Non-functional [Reply] button showing on mobile web, so that would make sense).

I can’t reproduce it, either. Thanks for rechecking it!