Forum Moderators: open
doesn't have much of a profile as an active crawlerIt's harmless. Within the present calendar year I find a whopping total of 22 Mojeek visits across three sites, each of them robots.txt + one page. One of those was a 410 from ten years back, another was for an URL that has been redirected for pretty exactly two years--both suggesting that they're following some very, very old links.
reverse DNS is definitely the finer point, after all anyone can proclaim a UA.