In any given thread, there are two ways of replying.
[ol][*]Using the "Reply" icon in the title bar of each post in the thread[*]Using the "Post Reply" or "Fast Reply" button at the bottom of the page[/ol]
For example:
If you use the reply icon from a Mr. Lucky post, it adds a "(in reply to Mr. Lucky)" message to the end of your post, as expected.If you use the buttons at the bottom of the page, you would expect either no message or that it would indicate you are replying to the OP. Instead, it shows that you are replying to the last poster in the thread.

I'm configured for "Flat Style" thread viewing in the control panel, if it matters. in A pretty minor issue, I know, but one that should be fixed. Then again... maybe it's just me.