Separating trackbacks from comments should be configuration option

There are a number of reasons to separate out trackbacks from comments:

1. Better readability, continuity of comment threads
2. Less server load on busy sites (fetching comments and trackbacks can get heavy)
3. If split up, the comment tab would always be shown; the trackback tab might only show up if a trackback exists; alternatively, the "empty" state for trackbacks should list the trackback URL for the node
4. Enabling/disabling trackbacks per node would be conceptually easier to understand, since they would in fact be a separate "dimension" of a node

There are doubtless other reasons for this, but these are the most compelling.

I mocked up a demo of JS trackback tabs, but after discussing with Aaron Welch, decided that the tabs should represent separate server page loads or at least be configurable to be shown as "JS tabs" or "server tabs". We'll be figuring out a drupal-wide policy for this which will guide this kind of question....

To explain more about why JS tabs don't make sense for trackbacks, consider our conversation:

Aaron Welch:

keep in mind on a high volume site, sending all comments and trackbacks and having only 10% users view trackbacks is lot of extra badnwidth cost. just something to keep in mind, from a sysdamin pos