[suicas]

I think they mean that they add "reddit" to the end of the search strings they submit to Google. Often if you're looking for discussion on a certain topic it's a reasonable starting point for a lot of things.

[abhijat]

I think they can clarify best but maybe they mean that search suggestions are ending with the string reddit.

Eg if I type best linux distro the first suggestion often is "best linux distro reddit". It happens for me too.

[mohanmcgeek]

OP is talking about ending up typing "reddit" at the end of query

The fact that a lot of people are doing that is obvious from your observation that it's the first suggestion