I've just asked Fairphone a fourth time about this... I guess they both have trouble with understanding my English and that they really don't want people to repair their phones themselves. Anyhow. I can't see the socket being a problem to desolder, but maybe a small risk for accidental desoldering of some nearby SMD component. I will try it as soon as I get hold of a new headphone jack. :)
Best regards,
Linus