Interesting - I did not even know that old.reddit used a different search. I rarely even use the search (occasionally I will use it to search a specific subreddit and assume it is only searching post titles). I pretty much exclusively use old.reddit + customized reddit enhancement suite and on mobile use the app Reddit is Fun. Anytime I have to go back to vanilla new reddit it feels like a totally different site. I'm not even really changing the default subscriptions all that much either at all - often I browse without being signed in. The part I find the most odd is that even without signing in the "hot" algo seems to organize top posts occasionally differently between the two (old and new).