Is that a fair comparison? Reddit has a ridiculous amount of data to search through. I feel like if improving search was so trivial, they would have done it already.
Edit: Found this on reddit's wikipedia page:
"On July 21, 2010, Reddit outsourced the Reddit search engine to Flaptor, who used its search product IndexTank.[91] As of July 12, 2012, Reddit uses Amazon CloudSearch."
It seems to be an implementation issue, not a technological one.