...isn't 5% almost exactly the Lizardman Constant? (https://slatestarcodex.com/2013/04/12/noisy-poll-results-and...) [Edit: my point being that the percent of people with strong non-standard gender preferences might well be less than 5%, so I doubt you'd be turning 5% of your user base away.]

Also, just to play devil's advocate, there are some people from the other side who could theoretically be annoyed by new pronouns as options and refuse to use your service because of it