MicoSelva
backlog digger
The answer is going to be 100% unsatisfactory to you.
As originally written, all references to Memorious used a male pronoun. During the voice actor casting process, Dave asked me which characters could possibly have female voices, and in a rushed email, the list I sent included "Memorious" (who is obviously not a voiced character in the game) rather than "Memento," who is. After Dave cast a female voice actress for the role of Memento, he changed the dialogue a line of dialogue, without mentioning it to me, probably assuming that my email meant that Memorious was also female. (Of course, Memento could have been voiced by a woman with Memorious being "male," as with Factotum/Factor.) Unfortunately, he left unchanged other references to Memorious being male. I didn't catch the incongruity until the mega-patch that James and I made in 2014, but by then there was no way to fix it without recording new dialogue, which we didn't want to do.
The Spanish, French, and German subtitles have Memorious back to his original gender.
I believe there is a similar incongruity with the Greeter, which may actually have he/she/it all used at various times.
Thanks for the answer. Male, then.