My understanding:
Technically, you can’t have two separate “for sale” posts. A link to sales post is fine. You are allowed to have a sales post and link to it in your “sig”. There is nothing in the rules stating specifically that an OP of a sales thread, or anybody else, is not allowed to link to a sales thread.
I think it helps to understand why the rule was implemented. Back in the day, if you had a “for sale” thread, it would show up at the top of page one in the exchange when posted. With no responses to the thread it would quickly fall to the back pages. To get it back to page one the OP would post “bump” (or anything else) and it would get “bumped” back to page one. People were endlessly “bumping” their own sales thread to keep them on page one in the exchange. To end this practice they changed the software and rules. Posts in a “for sale” thread no longer caused it to be “bumped” to page one of the exchange. The response was for people to post a “for sale” thread, if there were no responses after a few days they would post a new “for sale” thread for the same knife to get their sale back to page one. This caused a rule change - you have to wait two weeks before reposting the same knife.
The above post is technically a violation of the rules. However, my feeling is that there is no real problem because the above post is an exact copy of the post in the exchange and they were posted at the same time. IMO this does not violate the “spirit of the law” but is a violation of the “letter of the law”. A link would have been fine.
My opinion means nothing.