Where can you edit the display properties/layout for comments?

By this I mean the text that says "1 Comment" (or whatever), "Add A Comment", and the Name, Date, and comment text display itself. I want to change the text style and some of the alignment properties, etc.

I've been able to change the input form at comment_form.php, but for the life of me cannot find the above.

Look at the comment form plugin

As far as I can tell, that only handles the form itself, not how existing comments are displayed (also the "X Comment(s)" or "Add A Comment" texts). What I'm looking for is a way to control the font size/style/etc of these.

Or am I wrong on this?

The exact positioning and layout of this would be in the theme files - look at the files for the theme you're using (album.php, image.php, pages.php, news.php) and see where these functions are placed. You can play around with those files to control how the pages are displayed to the user - you won't need to modify the core files, as they control the functionality, not the presentation.

Styling is done via the themes CSS. You don't even need to modify the comment_form plugin as that plugin even excepts theme based custom comments templates. Just put the file from comment_form.php (that within the comment_form folder) into your theme's folder.