It's possible to post to a user's status, but it's difficult to abide fully by LinkedIn's API terms for what you're looking to do. For reference, see their Share's API documentation:
To make that post, you'd need to adhere to:
As with any API that allows you to post on behalf of a member, always ensure that the user is fully aware that your application is sharing content on their behalf.
JLinked can easily help you to add, with just a few lines of code, a post to the user's LinkedIn status. You'd be responsible for somehow making the user aware that this post is going to happen.
If you would like more information on how to do it, let us know. We can provide the PHP that you'd need to execute, but you'd need to dive into Kunena to know best where and how to implement it.
Hope that helps explain,