This is something I've longed for but have never seen it in any text editor yet: the ability to simply select markup tags and/or their enclosed contents. Most editors follow the selection logic of word > line, which IMO is rarely useful in working with code.
What I'd like is an assortment of modifier-clicks (command-click, option-click, command-shift-click, option-shift-click, etc.) that perform the following:
(when the pointer is inside a tag) - single-click selection of the current, single tag - single-click selection of the current tag, its corresponding opening/closing tag, and everything in between
(when the pointer is between two tags) - single-click selection of everything between the two most immediate tags (and excluding the tags themselves), with perhaps additional clicks casting wider and wider inter-tag selections (going from <td>[selection]</td> to <tr>[<td>selection</td>]</tr>, for example)
Some items (like the <div> tag in HTML syntax mode) are already being treated as collapsible objects now, but there's no way (AFAIK) to grab such an object and move it around without carefully selecting the whole thing character-to-character. This seems like a needless restriction to me.
Hope that's helpful.
John