Inria Sans has very similar glyphs for 0 and O. Since tags frequently use these characters, it may be very confusing. I suggest changing the default template font settings for tags. For instance, enabling the "onum" font feature makes 0 less tall (this is possible via CSS). Changing the font altogether is also an option.
This is a good idea; would you make a patch for the base theme that I can apply?
Hmm, no. Although Inria Sans has this font feature, the particular distribution in the theme does not include it. Is it better to replace the files with the complete version (which will make it larger), or choose another font? I tried it out, and the onum feature looks a little bit messy in the context because it has variable height. Using a font with the slash-zero variant might be better.
What if we try another font for tree IDs? For example, the Iosevka font has nice zeroes. But I'm open to other ideas :)
A more convenient thing to do is to just use the browser default monospace font. This is already the case with
\code{...}, so I guess that's consistent. Monospace fonts usually go out of their way to distinguish O 0 I l 1 etc.
good point! I think we should try that.