I think only the admins of the instance and mods of the community (and you) can delete your comment. Afaik your comment is only cached on other instances.

Reports go for admins and mods I think too https://lemmy.cloudaf.site/post/59357

Anyone can create a community. From the looks of it, sync doesn’t support it yet(?). But if you go to your instance on your browser you can create it from there on the top right settings.