Like this:
AI-generated summary
The discussion revolves around nested replies in Discourse. Zard_W initially asked about a plugin for nested replies, but Moin clarified that it’s a core feature. Zard_W then inquired about the “embedded-replies” section, which doesn’t work for them. awesomerobot explained that the feature Zard_W is referring to is actually quoting text.
Merefield pointed out that when quoting an entire post, the system removes the quote, considering it unnecessary. Moin added that this behavior can be changed by modifying the remove_full_quote site setting. Merefield suggested using the “Quick Quote Theme Component” for an alternative quoting feature. Zard_W thanked Merefield for explaining the function.
Hey @Zard_W Welcome to Meta!
It’s part of Discourse core.
There are some settings which hide the indicator under certain conditions:
thanks for help! 
@Moin How about this section?
It’s embedded-replies? but doesn’t work for me. 
do you mean this? that’s a quote — you can do this by highlighting text and selecting “quote”
You’ve quoted the entire post, so the system believes that is gratuitous and pointless because the reader can see the post just above and read it in full easily, so it removes the quote.
When you run a site for a while and see people regularly quoting the previous post in its entirety, you will understand how nice this is: it is just a complete waste of space!
And if you don’t like it you can change the remove_full_quote site setting.
Removal of full quotes from direct replies
You can try this Theme Component
Thanks a lot, I totally understand this function.