there are definitions that group various characters. In the browser, and when I copy that line to my editor, most of the characters are displayed as boxes.
As you venture out into the less frequently visited areas of Unicode, the environment you’re using will determine how the characters are rendered. The number of empty boxes (aka “notdefs”) that you’ll see depends on how many fonts you’ve installed, and your operating system, among other things.
On Discourse, the theme you’re using (as set in your Preferences) determines which font you’re likely to see. If you use the Dark or Light themes, you’ll probably be served JuliaMono - your post looks like this to me (no boxes):
On my Mac, those themes display using mostly Menlo (which is Apple’s hacked version of DejaVu which they used from 2009 to 2015). On other OSs there’s a good chance you’ll see Consolas. But other fonts will be used if necessary.