One of the attributes that you can set for any form element using Drupal's FormAPI is "#disabled". This effectively disables the form element - in most browsers, the user actually sees the element "greyed out" and is unable to set focus on the element.

The "disabled" attribute for form fields is a great little user interface helper that you can use to help protect data from accidental changes. It locks down an HTML input form element so that it can be viewed, but not be changed. This is handy when displaying a form to a user where you need an extra layer of protection for the data.

What happens when the user goes to submit a form with disabled elements? The value of the disabled elements are not passed back to the browser - this can quickly turn into a data validation and/or submission issue.

Adding form fields to a Drupal form dynamically is not the most straight-forward task. You'll see this occasionally on a Drupal form (poll module jumps to mind) when there is an "add another" button that (seemingly) simply adds another set of input elements to the form. The big sticking point in setting this functionality up is doing it in a way that keeps FormAPI's security intact. Fortunately, there's some tips to get you mentally started.

One of the most frustrating things about Drupal's current architecture is that comments, and the form to post them, are attached to nodes and don't easily allow you to move them around in your TPL files. There really should be an easier way to just place them anywhere you'd like. Most times this doesn't get in your way, until you want to do some fancy layouts where your content is split into multiple columns on the page.