One of the big mysteries of the software industry. Not specifically singling out reddit here, since I don't even search on reddit: Why can we not simply have search functions, that at least optionally do a substring search? If I had a $currency-unit for every search that fails at this basic thing, I wouldn't need to work any longer.
Search the same thing rephrased slightly differently 5 times to find the right result, and I can show you 5 sets of ads related closely to the topic of your search.