I you can add a custom font face if you edit your product or blog post text as HTML. Just add something like <span class="my-font-face"></span>.
Not very handy I'm afraid but it will work.
With some crafty Liquid string manipulation you might also be able to do this in Liquid as well. There's a lot of caveats in that approach.
I am indeed referring to HTML figures where you have an image and a figcaption. I've never heard of emojis being called figures.
There is also the issue with determining which images and text should be inside a figure and which should just be an image with a paragraph after it. I'm not sure how I would do that without implementing some sort of identefier that the user could put in to signify the start and end of a figure, which wouldn't be much better than just teaching them HTML.
Sorry, my bad. But it remains the same issue. Without hardcoded markup you can only parse and hope that some unclosed tag or crazy nesting will not break the parser.