There is a "Show Preview" button under "Preview page with this template". Could you explain cases when that is not sufficient?

Because I do not speak about a preview of transcluding page, but the code itself.

I don't see the value in this request myself. In what way does the textarea not contain all the code that's going to be saved? How would a preview of the rendered code change things?

Same reason as you have it on other ace content models.

Happy to consider a "Disable the pointless preview button on non-interpreted content types" task instead, then. Ideally it'd be shown but disabled to meet our modern UI design standards for the past few years, but by the time someone gets around to this we'll have likely changed those. :-(

:-) Please don't. It's just unconvenient working without preview. Can't use browser tools. Can't see long lines. Can't work normally with RTL string content. And so on and so on.

I agree with James. it seems to be pointless.

And also, of course, can't work in <> mode.

Now that links are made clickable in code comments (see T368166), I would like this request to be reconsidered.

For instance, by being able to preview, I would have detected this mistake very easily.