The way we have conversations on forums has not changed a lot on the forum software since the inception of forums. vBulletin tried something different with a major redesign, several years ago, but the software itself was so flawed that the concept itself did not take off. So I am at the stage where I need to take this decision and I thought of checking what is the general opinion. Hope to get unbiased and thought through answers. 
So lets look at the various options:
Option 1 - Conversation with only one level of nesting for each post if there is a reply/quote
Examples - StackOverFlow, Facebook, Youtube
Pro - keeps the main conversation in context and any off topic discussions can happen in the branch
Cons - Can't think of any as of now, so personally leaning towards this model
Thread
- post 1
-- reply 1
-- reply 2
-- reply 3
- post 2
- post 3
-- reply 1
-- reply 2


Option 2 - Conversations with deeply nested replies for each post
Examples - Reddit, Quora
Pro - Conversations are deeply nested and the context is followed down the nested tree
Cons - Can become a nightmare to navigate with multiple levels of nesting
Thread
- post 1
-- reply 1
--- reply 2
---- reply 3
----- reply 4
------ reply 5
- post 2
- post 3
-- reply 1
--- reply 2

Option 3 - Single flowing thread with quote/multiquote replies and posts
Example - TechEnclave or any forum software out there
Pro - Old school style which has been in use for over 20 years
Cons - A thread can get derailed with multiple off topic conversations happening simultaneously OR users completely avoid small talk so as not to derail the thread
Thread
- post 1
- reply 1
- reply 2
- reply 3
- reply 4
- reply 5
- post 2
- post 3
- reply 6
- reply 7
No screenshot needed

So lets look at the various options:
Option 1 - Conversation with only one level of nesting for each post if there is a reply/quote
Examples - StackOverFlow, Facebook, Youtube
Pro - keeps the main conversation in context and any off topic discussions can happen in the branch
Cons - Can't think of any as of now, so personally leaning towards this model
Thread
- post 1
-- reply 1
-- reply 2
-- reply 3
- post 2
- post 3
-- reply 1
-- reply 2


Option 2 - Conversations with deeply nested replies for each post
Examples - Reddit, Quora
Pro - Conversations are deeply nested and the context is followed down the nested tree
Cons - Can become a nightmare to navigate with multiple levels of nesting
Thread
- post 1
-- reply 1
--- reply 2
---- reply 3
----- reply 4
------ reply 5
- post 2
- post 3
-- reply 1
--- reply 2

Option 3 - Single flowing thread with quote/multiquote replies and posts
Example - TechEnclave or any forum software out there
Pro - Old school style which has been in use for over 20 years
Cons - A thread can get derailed with multiple off topic conversations happening simultaneously OR users completely avoid small talk so as not to derail the thread
Thread
- post 1
- reply 1
- reply 2
- reply 3
- reply 4
- reply 5
- post 2
- post 3
- reply 6
- reply 7
No screenshot needed