To my knowledge, there is very little regarding guidelines/rules from the Fiverr editorial team. My best guess as to why this isn’t in the ToS is that the editorial focus can change swiftly, especially if there is a new problem with a particular service. For example, when Amazon began to sue Fiverr sellers for putting paid reviews on Amazon, Fiverr wisely made a rapid choice to drop those gigs from search first and then they began to gradually remove them as they were able.
Since this can occur quickly when a third party company changes it’s own Terms or policies, Fiverr has to be able to alter their choices fast. Not all search issues are due to this, but since you specifically asked about editorial focus that’s what I’m trying to respond to. I would say it is for “no reason.” If a seller asks about a gig and Fiverr deliberately dropped it, the typical response from CS usually goes something like this:
“The service you have offered on Fiverr is not in our editorial focus and guidelines. Your Gig will not appear in our search results. You’re more than welcomed to submit new gigs via your Fiverr account and continue to offer new and unique services for future evaluations by our editorial team.”
I’ll also display a real example of a response received by a user based on this question, which is the most official thing I know of and comes from an older forum post. Based on this type of response, my suggestion to you would be to go with what Fiverr CS suggests and work on new gigs that are in alignment with currently promoted services.
Another way to go about it is to simply avoid putting up gigs that are connected to third party sites such as Facebook, Twitter, Google and of course to check the Fiverr ToS before putting up any gig. Not all third party associated gigs are a problem so I’m not saying you can’t utilize them at all, just suggesting one way to avoid being dropped from search.