[anacreon]

Thank you all for your inputs. I've just checked the database with kobo utilities, and it is ok.

@rev bob: the way it worked was perfect for me and needs no fix IMO. I have worked on Georgia for instance to make it blacker, and would not like to have to redo it every time I choose Georgia.

Since everyone else has no problem, I might try a reset, but it is a long and painful process which I will wait to be back home to try. Also in other cases (wifi for instance), it didn't work for me. OTOH, I feel like it is not a bad thing to do now and then, just like defragmenting my computer, considering all the to and fro-ing I do.

EDIT: I just checked on the aura 6" (I wouldn't go 3 weeks on holidays far away from a bookshop without a spare), and it is as before. I gather it is a problem on the HD, even though the data base checks ok. Definitely a case for a reset.
Sorry not to have done this before - I learned things about the fonts management from Jackie_w though, and might try to save the config file.