cweiske @pfefferle demanding strictly ordered + laid out HTML makes things easier for consumers at the expense of publishers, which is a known anti-pattern. We should optimise for ease of publishing.
Also, many implementations are already parsing the target HTML for reply-contexts (e.g. Aaron Parecki (example), @jschweisnberg (example and myself (example)), demonstrating that parsing HTML is not a significant barrier.
@benwerd IIUC, it's actually a special permalink page created for that line with a few additional lines of context. There isn't a good solution yet for sending a webmention from a page that has multiple h-entry elements. One possible solution that we've discussed is for a sender to send source URLs with an id fragment that a receiver can use to only parse #microformats starting from that id.