#TIL (Today i learned) and did not find within the documentation: You can use #hotkeys here:

• j - jump to next post
• k - jump to previous post
• m - expand the current post
• c - comment on the current post
• l - like the current post
• r - reshare the current post
• o - open the first link in the current post
• ctrl+enter - send the message you are writing.

Found it in a comment from @Waithamai Dragonqueen.