Nope
MacOS
1.0.12
No
No
Margin/Padding is fine with <div>, but messed up with <p> tags. Unfortunately Outlook seems to use <p> instead of <div> for new paragraphs. In Gmail this renders just fine.

Hey! Thanks for reporting this - will see if we can get this fixed in the next release.
Based on https://www.emailonacid.com/blog/article/email-development/paragraphs_in_html_email, I think it's safe to remove the default margin/padding from <p> tags all the time (it's what Yahoo mail does already.)
Hey folks鈥攖he fix for this has been shipped in 1.1.2. The app will auto-update in the next few hours, or you can download the new version directly from https://getmailspring.com/download. Enjoy!
Based on https://www.emailonacid.com/blog/article/email-development/paragraphs_in_html_email, I think it's safe to remove the default margin/padding from \
Why is Yahoo's behavior being taken into consideration? It represents 5% of the market. In the meanwhile, the giants, Gmail + Apple + Outlook = ~86% of the market, have margin around paragraphs, the way it's supposed to be. Market share source.
The link you posted is for people who write emails, their advice doesn't apply to email rendering.