The CAA (UK) does not require the Captain to countersign your flights (had a chat with an FCL guy the other day). The IAA however requires every hour to be countersigned that you count towards the TT1500 or the 500MPA.
As the JARs are not law, but recommendation only, states will have and keep their very own rules. So are for example the LASORS unheard of outside the UK.
regards, IP