@bes Implementing # in federated social software (and for you to be able to receive these, which requires some added metadata to your static HTML pages) would solve this issue. WebMention is an improved form of the "pingback" system bloggers may be used to. Pingbacks could work as well probably.

And cross-posting is not necessary if you have an RSS/Atom feed, since they can be subscribed to via any WebSub/PuSH hub (you don't have to run it on your server, an external service can take care of WebSub/PuSH).