@Sarah Brown
Like, you can federate full blogposts and suchlike, but Mastodon will strip away all the inline images and then just display the first 4 in a grid at the end.
The last four, actually. In reverse order even. At least in the cases I'm aware of.

At least you can circumvent this on Hubzilla by writing long-form stuff with lots of embedded pictures not as posts, but as articles in the "Articles" app. Mastodon users will only get a link to the article which will then open in their Web browser which, in turn, will display it the intended way.

It's still a pity that you have to take such measures and refrain from using the features Hubzilla offers at post level to their full extent because that'd confuse 12 million users of a deliberately feature-lacking project. And users on, for example, Friendica and (streams) aren't so lucky because they don't have a separate long-form-writing method at hand and have to rely on external projects like WriteFreely which means one more account and one more login. On top, there's the effort of following your own blog and resharing each new blog post notification to your followers because not even 2% of them will follow your blog. Not to mention countless whining iPhone users because they have to have Safari start up to read your long-form posts.