Posted 02 April 2012 - 08:50 AM
With regards to post caching, it should be noted that you can disable this...however this is a case where extra queries on one page load are typically entirely worth it on subsequent page loads.
Parsing bbcode is an expensive operation - it's just the nature of the best. You're looking through text strings, often using regular expressions, and plucking out bbcode to turn into HTML. When you allow posts to cache, the parsed version is then stored and later used when the page is displayed (up to 7 days by default as you noted, though you can cache longer if you wish, but remember as with everything there is a balance to maintain). As mentioned, you can disable this caching...but the savings you get on subsequent page loads are much much greater than the few milliseconds it takes to insert the cache.
Reputation is a different matter, and as Matt noted, that is primarily because you converted - in normal operation, the inserts you are seeing are stored as the post is made, so you would not typically have all of the reputation caches building on view (but rather, on initial save).