[Feature] Display invisible characters

[ErrorSource]

Would it be possible to show invisible characters like tabstops, whitespaces and new lines (especially on active line and in code-blocks)?

Like:

[CharlesButcher]

This would be really useful, as would a feature to clean up multiple spaces and blank lines, which I've seen somewhere (Scrivener?). I know those shouldn't matter much in Markdown, but sometimes we need to copy plain text…