The evidence is against you here, as almost all known usage of webmention has been for short replies which don’t make sense without context.

Actually we aren’t disagreeing, maybe I didn’t express myself well when I wrote “At the moment of the method is built around a POSSE architecture. This works well for long form articles which can stand alone but address issues or ideas that are posted on an external website”.
What i meant to say is that Indieweb replies make no sense outside their context which makes it counterintuitive to be posting them and displaying them via POSSE. Of course it can be done (and I like the concept) but i doubt it will catch on. Whereas a long form artcicle replying to another doesn’t really need the context as it stands alone.
I agree that webmention is nicer than pingback and your work on the toolbelt is awesome.
With respect to my external comment idea, there is no security hole, most commenting systems allow commenting without logging in and it is up to server on whether it accepts the webmention of the comment posted. Finally like webmentions itself it is a chicken and an egg thing whether PESOS webmentions would catch on. Without modifying existing implemenations it won’t work.  I’m slowly getting the hang of Github so I might fork Matthias’ plugin and build it myself if I find the time.

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More importantly though webmentions vision includes distributed commenting and it does succeed at making this possible, and members of the community are making use of this functionality. However the current workflow is awkward and i doubt it will catch on with the general public. Sophisticated Indieweb users can and will read an article on an external site and then return to their own to post a comment, but that king of behaviour is not intuitive.
But all is no lost as the webmention protocol could easily be implemented to support PESOS, which when commenting is more much natural. This is best explained by illustrating a use case namely:
A commenter (for this example me) arrives at external site, reads an article and wishes to make a comment. I make the comment on the external site and as part of making the comment I add my author url, that being the url of my own site. The external site then sends a webmention of the comment to my site. My own site could then scrapes my comment and saves a copy in my CMS. Otionall  I could republish the comment in my blog or activity feed at my discretion. Thus fully implementing PESOS.
This article is hopefully also posted on IndieNews. Also mentioning Barnaby Walters for good order.

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I need some more details on how to install it. Do I just upload to the plugins folder and then modify the code in the comments template of my theme?

Any help is greatly appreciated.

In reply to My Webmention plugin for #WordPress……

In reply to My Webmention plugin for #WordPress…

You can now also reply to my comments 🙂 #whoot

ok, let’s try a second one!

I just implemented replys… I hope this will work…

(please don’t answer, this feature isn’t implemented yet 😉 )