An other thing to consider, is the persistence of links, or lifetime of links.

Links (in posts) on most social medias are very shortlived, because they get buried fast, and even more shortlived if the post is on the border or outside the rules since it gets removed. 
So the people seeing, and maybe going through the link, are limited to the ones who see the post shotly after it is created, since little after, that post is nowhere to be seen.

While any link which remains always visible (most of the times not inside a post, but in the headers or menus of sites, in the places which can't be buried), may get less people through it at the same time, but it stays effective for much longer, and on the long run it may bring in more people than a short wave from a shortlived post on a popular place.
Though, slow flows of newcomers from stable links are usually not enough to build activity, so it's better to don't rely on a single stable and visible link, but more of them together, even if from different places.


An other obvious thing, is that visibility is important to get new people to visit and have a look in, but visibility is only half of what brings new actives.
The other half is content, what the visitors see, and what interests them enough to remain and add something.

About content, in my experience, it brings more discussion to state something rather than asking something.
It doesn't matter if the statement is perfectly correct in everything and flawless, any mistake or overlook is a chance for a correction, which the correction itself is also part of discussion, though not all of it, it becomes just aimless to only have corrections, but eventually the discussion can also develop past the mistakes.