A little SQL fiddling on the query - This one shows the computed weight and factors for comments (sorted by weight, then creation date).
The top N rows in the results are what will be shown (where N=5 for main sites, 15 for meta) - I'm using Creation Date as the tie breaker value when multiple comments have the same Weight. Everything else would be behind the "view/add more comments" link.
TODO (for someone feeling ambitious): Play with tie-breaker algorithms.
It's possible that Score would be a better tie-breaker than Creation Date.
A modified "weight" (just summing score, length, age) may also work well.
