There are two possible reasons why you may not be able to personalize a post.
If you can't edit the text when you select 'Queue' or 'Share', this means that the program manager has disabled editing for this post. You will notice that for these posts, they are only available to be shared to LinkedIn. This is to comply with Twitter and Facebook's new sharing policy that requires personalization before sharing.
If you can't see both the 'Queue' or 'Share' option, this means that the program manager has disabled these options to make this post visible to internal employees only.