Markdown edits breaks page when using special editors like Textwrangler (indent)

When I use my editor of choice (Textwrangler on mac, haven't tried it on Notepad++ yet) my markdown quite often gets corrupted. mostly because the amount of spaces gets screwed up.
Why is the amount of spaces even relevant? Shouldn't be the hyphens be enough? This makes troubleshooting after large edits really messy.

The YAML in frontmatter is quite space sensitive. Indents rely on usually either 2 or 4 spaces, and can't be tabs.