Out of the box, XenForo does not support deeply nested (threaded) replies in forum threads. Posts in a thread are typically shown in a linear order.
According to a XenForo developer (Mike), there’s no “parent post ID” tracking for internal threading, which makes native deep threaded mode difficult.
For a thread’s reply-section (i.e. replies to replies), someone on the XenForo forum asked for nested replies; the moderator said it requires custom development.
How to Add Threaded / Nested Replies
If you really want a threaded/nested reply structure, you can use add-ons:
[XB] Post Comments: This is a well-known add-on for XenForo. It lets users reply directly to a post, and displays those replies nested / inline. You can set how deep the nesting goes.
XenForo Nulled Community
+2
XenVn.Com
+2
Forum Comments System:
In XenForo’s own Q&A thread context, people have suggested nested replies (especially for “Answer” type threads) so answers can have comment threads under them.
Pros / Cons of Threaded Style in XenForo
Pros:
Better clarity when people reply to specific posts (not just the original thread post).
Cleaner “sub-discussions” — replies to replies stay nested, rather than dumped at the bottom.
Cons:
More complex interface / UX.
Potentially more work / cost (if using add-ons or custom dev).
May interfere with some XenForo features (multi-quote, “quick reply,” etc.). As some devs have pointed out.
Bottom line: Yes — you can have a threaded-style view in XenForo, but not natively. You’ll need to rely on add-ons or custom development.