The bug with “BS” code when edit markdown

[liuzhaowei55]

• VSCode Version: Code 1.19.1 (0759f77bb8d86658bc935a10a64f6182c5a1eeba, 2017-12-19T09:35:14.671Z)
• OS Version: Darwin x64 17.3.0
• Extensions:

Extension	Author (truncated)	Version
beautify	Hoo	1.1.1
crane	Hvy	0.3.8
vscode-eslint	dba	1.4.3
vscode-html-css	ecm	0.1.8
vscode-great-icons	emm	2.1.22
phpcs	ika	0.7.0
php-cs-fixer	jun	0.1.54
vscode-JS-CSS-HTML-formatter	lon	0.2.3
Go	luk	0.6.70
dotenv	mik	1.0.0
debugger-for-chrome	msj	4.0.0
php-docblocker	nei	1.3.3
vetur	oct	0.11.5
laravel-helpers	raf	0.2.2
laravel-5-snippets	sac	2.0.1

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Steps to Reproduce:

1. 编辑 markdown 文件时，有小概率在按退格键的时候在正文中产生 “BS” 退格符号。挺严重的一个问题，希望重视。

Reproduces without extensions: Yes/No

[liuzhaowei55]

Just like this issue ,this copied from vscode bug report window, the "?" I think it's "BS" code,I used "backup" in there.

[mjbvz]

Duplicate of #37114