Thanks for trying it out! would you mind giving some steps that allow me to repro the issue? It's early days so i'm sure there are some rough edges, hopefully I can fix them quickly.
https://github.com/chaoxu/coflat
Mine also have lot of bugs (especially reader and editor doesn't completely match yet).
repro the issue: click random places and add random texts, scroll around, and issues come up sooner or later.