Availability: all channels
Email: creates an indented quote block.
Slack: The text is indented, and italicized in accordance with Slack formatting.
SMS / Direct Message: The quote block text is automatically inside quotation marks which can't be deleted.
Facebook Messenger: Text from quote blocks in other channel types is available, but when moved from the Library into a Messenger notification, it is unformatted (but editable like a text block).
Filter out a Quote Block
Like with any content block, Quote Blocks can be hidden using a conditions filter.