The Hypothesis client supports a query syntax that filters the cards displayed in the sidebar. For a given URL, e.g. http://example.com, you can focus on threads involving a particular user, e.g. Jane, like so: https://example.com#annotations:query:user:Jane. This tool automates the construction of those links.
To focus on users contributing to discussion on a particular URL, specify the URL. If the annotations are not in Public, also choose the group. Then click search to produce a per-user link for each user who has annotated the selected URL in the selected group. Click each user's name to launch the Hypothesis client in a mode that focuses on threads involving that user.
If the group you choose isn't the sticky default in the Hypothesis client, you'll need to make it so. If you specify a group other than Public, you'll need to provide your API token to read from that group. If you don't specify a URL, the tool provides per-user links for all URLs annotated in the group.