Instant Smart Quotes от Rita Skeeter

Replace typewriter quotes, apostrophes, ellipses and dashes with their typographically correct counterparts as you type.
Instant Smart Quotes is the last extension you will need to write beautiful typographically correct texts.

• Support for over 50 languages
• Quickly enable and disable the instant replacements from the toolbar
• Quickly change the language from the toolbar
• All settings are saved per page and synched across all of your devices
• Text in backticks will be ignored in favor of Markdown

Depending on which language you have set, the following chars will be replaced for language-specific replacements (comma-separated):
', ", >>, <<

Chars that will be replaced for no matter which language are the following (comma-separated):
‘, --, ---, …

This website is a nice manual for English punctuation guidelines:
http://www.thepunctuationguide.com/

Sources of which quotes to be used for which language:
https://en.wikipedia.org/wiki/Quotation_mark#Summary_table
http://www.witch.westfalen.de/csstest/quotes/quotes.html

"Don't be dumb", “you’re using Instant Smart Quotes”. ✍️