According to the tooltip of the 'interesting' tab, interesting questions are
"questions that may be of interest to you based on your history and tag preferences"
Does Stack Overflow use a recommendation engine or just some sql sort/filter?
migrated from stackoverflow.com Oct 25 '12 at 10:28
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In short, first drop any topics you ignored or attract low-attention, then apply the scoring formula:
Those make 90% of the interesting questions. The other 10% comes from some random pick.
It's a simple but effective solution.