I'm not sure how it would be done technically (it might be possible), but one risk is that if there's a deletion or removal of posts from a topic, the numbering would get out of whack. That said, each post is automatically numbered from the POV of the forum itself. Your opening post in this topic was 26392.
If I want to refer to a post, I will usually do so by way of a URL to the post itself. If you look at the heading of each post, it's actually a hyperlink, inclusive of a URL.
Live in concord, with mutual appreciation, without disputing, blending like milk and water, viewing each other with kindly eyesDhamma Wheel (Theravada forum)
* Here Comes Trouble