comps in query

An agent at a webinar I did last year said that if the self-pubbed author has had mega-sales, then it's great. If not, then stick to trad published comps. HTH.

It's important to remember that when you're making these comparisons, the ultimate goal is provide a kind of narrative shorthand for what kind of story you have, and what kind of audience would like it. So if you're citing obscure titles that might force the agent to dig around just to find out exactly what you're referencing, you may not be doing yourself any favors.

Just don't also do the opposite and call your book the next Twilight Meets Harry Potter Meets Lord Of The Rings Meets Every "The Girl" Novel.

Yeah, unless they sell a lot/are well known then don't compare to a self-published author. Essentially, the agents are trying to gauge the markets that might be buying your book, but they also use it to see if you are well-read in that particular genre. If you compare it to Lord of the Rings and Harry Potter then they will think you haven't read much in this genre and it is likely to descend into old, old, boring cliche done a thousand times unto death. Nor do you want obscure niche titles. You really want something thematically similar in some way that is decently known but not mega-famous.

I think it depends on the sales. If it's an established bestselling, self-published author, then it's probably fine. Otherwise, it's best to stick to traditionally published works.