quilljs/quill — pull request #270 by thomsbg (2014-12-03 18:57:13+00:00)
Title: Fix backspace-at-index-0 behavior by ignoring negative start indices

Reproducible on quilljs.com by placing cursor before first letter and hitting the 'Backspace' key.

Expected behavior: nothing happens.
Observed behavior: the first character is deleted.