iPadOS 13+ sends a desktop Safari UA by default, which fools CodeMirror's mobile detection into using the more fragile textarea input mode. That, combined with CodeMirror repainting the line mid-composition, breaks Korean IME composition and leaves jamo unmerged. inputStyle can't be changed after the editor is created, so it must be set in the EasyMDE constructor options.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>