Whatever there was it's going to be irrelevant when we upgrade to the next version. This board is no longer supported, so, we are moving to the version that is.
From what I can tell, that exact feature will be in the newest version, instead of being a hack someone put together.
In terms of words like "hack" and "efficient" what I mean is there are right ways to create SQL statements and there are wrong ways. If your database wasn't designed with the feature in mind, you really have to make you system work hard to produce the results you want - and that is what the inefficient part is. That feature "Most Active Posts" was not designed into the system, so someone wrote a query that will do it - but at the expense of the database resources being consumed.
The latest version is designed to support this feature, and so I believe that it will perform better.