Yes, for name, comment (summary), and some other fields, many html tags and entities are supported. If there are other fields you are asking about, let me know what they are, and I can check for you. I don't think we have an exact list anywhere -- we tend to add them as we discover we need them. For the &; entities, we support all the greek letters and many others, e.g. plusmn, ge, le, gt, lt, reg, copy, trade, rarr, larr, harr, deg, dagger, bull and more. We also accept many accented characters, but convert them to the corresponding non-accented versions for display in the desktop software (some of the above-mentioned entities are also converted to standard ascii for display in the desktop software). The tags we accept are i, b, strong, em, u, sup, sub, h1, h2, h3, br, a, img. Other tags are accepted but ignored for desktop display.
If there are other tags or entities you need, let us know, and we may be able to add support for them, but probably not if they involve complicated formatting (e.g. tables, lists, grids, flexboxes). And we can't support css style directives in the desktop software.
If you run Pathway Tools as a web server, then any tags and entities will be passed through to the web output, even if they can't be displayed optimally in the desktop software, so it can still be worth including them.