Image captions in Markdown don't display correctly on GitHub

[worldofgeese]

Select Topic Area

Bug

Body

For example,

<figure>
    <img src="https://upload.wikimedia.org/wikipedia/commons/thumb/1/14/Un_hobbit.jpg/640px-Un_hobbit.jpg" alt="An illustration of a hobbit with hairy feet" />
    <figcaption>This is the image caption</figcaption>
</figure>

produces, in Markdown files and comments like this one,

This is the image caption

[TheGiraffe3]

The alternative text is what displays if you hover, I think. The figcaption therefore produces the caption.

[worldofgeese]

That is correct, however you can see that the caption is produced unformatted. It's not clear it belongs to the image and any following text after the captioned image does not respect line breaks.

[TheGiraffe3]

Can you use the formatting symbols? (_ _, ** **)