It is not shilling by the "letter of the law" because a shill post is an original post by definition.  

Giving someone a recommendation of another provider, is by definition, not a shill. However, it is very much a shill by a spirit of the law. The posts that you just pasted on the screen have gone beyond what most hobbyists consider a well meaning and selfless recommendation

but there is no real way to know that.

Nevertheless, I often will post something complimentary under the ad post of someone I know and like as a favor to them and a service to a prospective client, and not for any other reason.

a gal at all. That's just so sweet to see him all crazy bout a girl...!!