I think this is sensible. I've changed the code to only include articles and comments from the last 30 days. (The side box may not update immediately as your browser is likely to do some caching.)
Mea culpa. I hastily pushed that commit as there was a broken article on production that needed a hot fix. Embarrassingly, in my haste I deployed before the tests finished. Should be fixed now.
Strange. The calculation for total Karma has not been touched by these recent changes.