Each box represents a subreddit, The size of the boxes relate to the number of comments received by commenters of this subreddit. The proximity of the boxes to one another relates to the number of common users shared between those subreddits.
Results are heavily cached, so maybe showing data that is old.

You can search for a user using the search box by prefixing the name with "u/"

The following tech was employed:

This app was created by engineblock ltd.
Message the creator via Reddit