If the original quoted page changes, it could potentially send a webmention (technically a salmention in function) to all the pages that had previously mentioned it to create updates.
Automatic transclusion can also be more problematic in terms of original useful data being used as a vector of spam, graffiti, or other abuses.
As an example, I can “transclude” a portion of your page onto my own website as a reply context for my comment and syndicate a copy to Hypothes.is. If you’ve got Webmentions on your site, you’ll get a notification.
For several years now I’ve been considering why digital gardens/zettelkasten/commonplace books don’t implement webmention as a means of creating backlinks between wikis as a means of sites having conversations?
Note: I’ve also gone in and annotated a copy of Maggie Appleton’s article with some additional thoughts that Aquiles Carattino and others may appreciate.