Error accepting suggestions with multibyte (Cyrillic) characters (utf-16 -> utf-8 fixes the issue)

[Galicarnax]

When I type with Cyrillic alphabet, and getting suggestions, pressing the key binding to accept gives this error:

Error  02:24:02 PM msg_show.lua_error Error executing vim.schedule lua callback: /usr/share/nvim/runtime/lua/vim/lsp/util.lua:485: index out of range
stack traceback:
	[C]: in function 'get_line_byte_from_position'
	/usr/share/nvim/runtime/lua/vim/lsp/util.lua:485: in function 'apply_text_edits'
	...l/share/nvim/lazy/copilot.lua/lua/copilot/suggestion.lua:489: in function ''
	vim/_editor.lua: in function <vim/_editor.lua:0>

Looking into lua/copilot/suggestion.lua, I see this:

    vim.lsp.util.apply_text_edits({ { range = range, newText = newText } }, vim.api.nvim_get_current_buf(), "utf-16")

If I change utf-16 to utf-8, everything seems to work fine. Any reason for utf-16 here?