1) Bookings and suspensions related to domestic cup competitions being carried over to league matches e.g. Morata will be suspended for Chelsea's next PL match because of a yellow card he got in the League Cup win over Bournemouth whereas in other countries such as Italy if you get booked/suspended during a cup match then that only applies to future cup games.
2) Players on loan from one club to another in this country are not allowed to play against their parent club e.g. Zouma isn't allowed to play for Stoke against Chelsea. In other countries if a player is on loan from one club to another then they can play against their parent club.
In the cup game instance I'd say that we do it the 'wrong' way. Bookings from Cup games should only apply to cup matches as it's an entirely different competition, also managers might leave star players out of cup games if they're on 4 yellows as they won't want to lose them for the more important league match if they get a fifth caution. You might also get players getting cautioned on purpose in a league match if they know that their next match is a league cup game and that's when they'd serve a suspension.
The loan one is less clear cut. You could argue that the host club has paid for that player for a period of time so should be allowed to use them regardless of opposition. But then again there's an argument that the player might have a conflict of interests if allowed to play against his parent club. It's also a bit awkward when a loan player scores against their parent club (e.g. Lua-Lua against us before they changed the rule). Personally I'd say it's best that loan players can't play against their parent club as it's a bit of a tricky situation.
What do others think? And are there any other quirks in British football that we have which all the other major leagues don't? Surprising that UEFA or FIFA don't make sure there's standard practice on these things.