Hi Marco, great and very useful plugin, thanks!
One question: I am currently using your plugin on a bilingual website (English/Chinese) and I am using WPML to accomplish that feat.
In the string translations of WPML - after scanning your plugin for translatable strings - only two strings pop up, "Add New" and "Add Existing".
But when I am looking through your plugin files I see lots and lots of strings and you are using a call to the text-domain of "$cimy_uef_domain". WPML however does not pickup on that.
On the file
cimy-user-extra-fields/cimy_uef_register.php I have even tried to use another text-domain to see whether I could make it visible, but unfortunately that didn't work either. I was trying to make the line "Insert the code:" on line 1159 available for translation (for the visual verification code).
I am not sure what the problem exactly is, but I do know that WPML offers plugin developers support towards making their plugins compatible with WPML. Apart from that they also have a language configuration file that might be able to help you.
Please let me know if you need additional information.