I have some heading 3 levels in my Descriptions. They look bold in Edit Mode, but they are often not. You have to select each one and apply bold, and it looks the same. So I wound up with a lot of heading 2s that were plain text and didnt look heading-ish upon save.
Play around a little in different ways with them and you should see.
Which property are you having issues with? I'll have a look.
All. In description, heading 3 looks bold in edit mode, but is unbolded in view mode (after save)
Ahh, I see what's going on. The editor theme is slightly different than what's on the hosted site. The hosted site headers are a medium bold, not the very heavy bold shown in the editor. To my eye that looks better than the heavier bold which is why the hosted site theme does that by default.
Keep in mind also that listing sites are going to use a plain text version of that description.
If you want to bolden up the <h3>'s on the hosted site, edit the site settings and add this CSS in the Layout section:
h3 { font-weight: bold; }