The limitation of templates for web design changes
Given that DWiki is template-based, in theory I could fix my comment form design mistake from yesterday. All I would have to do is revise the 'write a comment' template that's used here so that it included the entry and the existing comment, as well as a preview of your new comment and the comment entry form itself.
Except not so fast, because this revised version would be a usability disaster as I've described it. The problem is that all of the links to the 'write a comment' page have no fragment identifier right now, so they go to the top of the page.
When the top of the page was either the comment entry form or a preview of your comment, this was the right decision; you immediately see the important thing, what you clicked on the link for (or the 'preview entry' button). But if I just changed the template to put the existing entry text at the top of the page, well, that's what you'd see. This would be a terrible interface; you would click 'add comment' and get what looked like exactly the same web page unless and until you scrolled down (possibly quite a bit). Given that websites are often broken, I'd expect most people to immediately conclude that something had gone wrong in my comment process and give up on the spot. And if you persisted, you'd get to scroll down again every time you previewed your comment (which you have to do at least once).
(I generally assume that most would-be commentators are not all that strongly motivated.)
Fixing this is beyond the power of DWiki's templates. While I could easily add a fragment anchor point to the 'write comment' page, the links to the page are generated by hardcoded logic that lives outside the template system. I could go fix the logic too, but this level of redesign clearly requires me to step outside the template system.
(Plus, I'm not even sure if you can
POST to a URL with a fragment
identifier. Probably you can, but I'd have to look it up to be sure.)
I suspect that this is going to hold true for most template systems. If they automate things like form creation at all, they are likely to contain assumptions about the possible shapes of your design and thus limit your ability to change it radically. You can flesh out the skeleton in many ways, but how the joints move is going to show through sooner or later.