Send a direct message - doesn't find existing user

I just wanted to send a message to an (ex-)colleague of mine (who is a member here - I verified ) and has been of the old SDN/SCN for years as well), however the system doesn't find him.

I tried searching on his actual name (first name + family name, family name + first name, with capitals, without capitals, userid in the SAP Community, ...) but he cannot be found. However, when I check the people that I follow, he appears nicely?! Unfortunately I cannot send a direct message from there...

I do seem to get a list of users I can send messages to, but that list is (extremely) limited (and apparently not containing all people I'm following).

Could you investigate please?