Here are a few features that I think would be good to add:

Administration & Moderation

  • Signup applications (under the Reports button in Inbox would be ideal)
  • View votes (afaik mods should also be able to view votes in their communities)
  • Perhaps some sort of administration panel
  • Merge “Admin tools” and “Mod tools”
  • View moderation & report history for users
  • Better modlog UI
  • Checks for whether or not some mod actions can be done on a user and hide options that can’t be applied
  • Add “Feature Post in instance” to posts

Create new post dialog

  • Rename “Compose post” to “Body” or “Text”
  • Pre-expand text field area
  • Add new field for thumbnail URL
  • Allow choosing post language

Create new comment dialog

  • Allow choosing comment language
  • See who you are replying to in addition to the comment content

Media

  • View & manage uploaded media
  • Add option to loop videos
  • Add option to unblur NSFW images when in NSFW communities

Other

  • More user friendly errors
  • Advanced search (search in community, filters, etc.)

Oh and the updated join-lemmy.org applications page lists that Summit has 2 GitHub repos. I think it would be less confusing to just link to the repo that contains the source code instead.