LinkedIn has changed the interface when sharing links in DM's.
If you receive a link/vaam in a DM on LinkedIn it will show you this:
If you click on the link/vaam it will show you this:
The four buttons marked in red are to LinkedIn and not to our platform.
If you click again and open the vaam it will show you this:
This means if you click on comment on LinkedIn's buttons (in red) you will share the content on your own LinkedIn page and it will pop up in your activity feed.
If you want to leave a comment on the vaam, click on comment (in green).
Or answer directly in a DM on LinkedIn.