I’ve just tested it. You just need to tag the community in the text of your Pixelfed post.
See here: https://pixelfed.social/i/web/post/587303441777627505 and here: https://bolha.forum/post/15364
No. Lemmy (and any other FediVerse service) can be targeted for take over from any corporation. But there’s a few things that prevents from thinks like… Idk, Facebook buying Instagram or Musk buying Twitter:
Tl;Dr: we are not free of corporate interest, but we have tools to prevent a corporate dominance.
Pixelfed has a “stories” feature. It’s only on the website version (no apps) and it’s labeled as “beta”.