When both seated at a table and in play, then all chats go 'To Table' even if you send your message to f.i. your partner.
When seated at a table then all chat addressed to one particular player, even the chat from 'outside the table', can be read by all 4 players at the table.
If you send a personal message to a player elsewhere in the club, while you are seated at a table :
◦the addressed player sees the message but not your table mates.
◦if the addressed player is playing at another table then the players at that table see the message
When you are both NOT seated and a private message is sent, then no-one else can read that message
All is set-up like this to prevent any form of passing on unauthorised information.
When you want to talk privately with another player, then it is best to not to be seated.