Atom syndication feed doesn't look great.

[RetroJimmyX]

When viewing a post from the Atom syndication feed (via https://pixelfed.social/users/RetroJimmyX.atom for example), I see the attached image.

1. Pixelfed puts the same text accompanying an image post in the title and summary. When there is a lot of text, the title becomes too large.
2. All the hashtags signs (#) prefixing words to use as tags are visible but not functional.
3. HTML tags are visible within the text, instead of interpreted.

I'm not a programmer but after some brief reading:

1. The title could be constructed using up to n characters and a ... suffixed
2. The # characters could be stripped out of the title. They could also be stripped out of the article text but this misses an opportunity for any viewers of the feed to be able to click on the tag and be taken to the pixelfed instance and see any related images with that tag.
3. There may be an issue with content-type (~ mimetype) when the feed is constructed where the text accompanying an image should be treated as HTML not TXT but then characters may need to be escaped out and there may be security implications.

Let me know if this does/not make sense and any further info required. Thanks in advance (and for such a wonderful package).