I wanted to suggest another approach to this feature, which I for one could really use:
Currently, you can link part of any rich text to an entity, very nice feature. When you do this, that quoted text shows up in the references areas of the entity it is linked to.
It occurred to me with an additional tweak, this feature could be expanded to handle most of the “Discourse quote” functionality:
If you could take the part of the rich text field that is being linked to, and move it via day drag and drop (not unsimilar to today’s discussion in 
Feedback needed: Drag and Drop blocks in rich text fields and documents) to a comment you are making in an entity that would be very close to what can be done here in Discourse by simply highlight text and having the quote auto-create.
Alternatively, if there was a way to include the text that is being linked right inline in a comment or Rich Text, this would solve the need as well.
And just to reiterate, my use for this is the need to often refer back to comments of my team across Fibery. We use comments liberally to communicate, so it’s often useful to point out to a team member these converstations, ideally with context. Right now the only way we can do this is to make a screenshot of the comment that you want to quote, then add a link to that entity. This doesn’t allow clicking back to the original part of the quote that we took the screen shot of, and generally is time consuming and a work around.
Thanks!