Flow/Architecture/HTML caching

Flow uses memcache to cache workflow items from the database.

The team is considering caching HTML for entire topics, and possibly entire Flow boards, for anonymous and logged-in users. Users with

Things that currently vary by user

 * The username/IP appears above textareas for any reply the user makes.
 * approach: don't show these in non-JS version ({{bug|do in JavaScript, don't y