My current employer is a global software company with offices in several continents. The company tries to maintain a culture of conviviality.
Our main communication medium is text chat in English ; every employee's legal name is displayed on our accounts.
In direct messages with co-workers from other offices (mainly software developers, such as myself), I tend to use first names when greeting them ("Hi Jo! About that code patch, ...").
However I have read that addressing someone by their first name can be rude in Korea (and probably other places too).
In direct messages, how can I greet co-workers from Korean offices without being rude, but without being too distant neither?
In company chat channels, shared with other members, what is the appropriate way to refer to a Korean co-worker: is full name appropriate?