A limit to posting may improve the quality of each post.
Though, a limit can be broken by people having more accounts.
The idea is that if you can only post a small amount of times,
you have to be more considerate in what you are posting.
And that does not seem such a bad idea.
As alternative one might give a karma penalty to people that want to post over
their daily limit. On some days there is a lot of news, and this limit would
make it impossible for some users to post this news.
For any limit, I also there should be a difference between insightful and fun posts.
This requires the submitter to mark a post as EITHER FUN OR INSIGHTFUL.
I think that it is very good for a site, and for the mental health of people, to have fun posts.
And then we have posts that you put in your sub to keep it alive.
A major draw-back would be when too few people would post to the site.
For this the limit might even be a number that varies.
For example a limit of 3 would give:
3 insightful posts anywhere
+ 3 fun posts anywhere
+ 3 posts in your subs combined (for moderator or approved submitter).
With the low traffic today it might be limited to 6.
And even a limit of 10 would give some psychological pressure to people.
If you want to post more you can combine it in a text post or add it in a reply to a related post.