A final update to close this out:
Done. #online-attendance has an icon to make it easily distinguishable.
This seems to be an issue in communication with Open Street Map that we can explore with the plugin author.
We may decide to integrate an external link option for the data that shows up at the top, but for now including an external link in the textbox seems to be working fine (pro tip: if you include the link on its own line, it creates a nice preview). Facebook sharing should work well now, although there’s still some discussion to be had about the feature of users’ avatars showing up as the image preview.
As mentioned by @qgil-WMF above, that’s this feature: Displaying / importing Wikimedia Space feeds in Wikimedia wikis.
With that, I think we’ve covered these suggestions. I’m resolving the topic, but if anyone has anything else to add, feel free to continue the conversation.