Outlook loves messing with messages. "Detecting and removing" extra line breaks is one of its features
All it took was going through configuration and disabling some features which intuitively looked like they may mangle my emails.
It is my belief of the issue at lot of people have with email stems from Outlook. One example is the weird instance of top posting has made it hard to read many conversations and fostered a mentality of firing of quick response, reducing Outlook/email to a poor mans IM client.
There's a ton of improvements that could be made to Outlook to make it better.
Another thing that Apple Mail does is to pick Unicode characters that don't map to ascii for quote and other punctuation characters.
If you view it in an ascii-only mail client you will see plenty of places where an ascii character could have been used but instead a visually similar code point has been chosen. Things like dashes, single and double quote characters.