There was a time that I believed this as well. Now, I no longer do.
There are at least five factors that will decide whether you get
a high reputation for your post:
- Whether the thread has been front paged.
- Whether you're one of the first replies.
- How deep in a thread you reply.
- The popularity of the subject of the root node.
- The actual content of your post.
And the importance is roughly in that order. The first four items
all have to do with how many people will actually see your post.
If only you could see all the reputations of all the nodes in a thread,
then you could compare. A reputation of 15 where all the other posts
don't get above 10 is likely to be better than a reputation of 25 where
all the other posts score 40 or above.