I've dealt with this for some time now, and happened to find this thread only because I was looking for an answer to the same question. I haven't found a definite answer that works...however, on my own I have just tried something but it will be a few days before I will have an idea whether it "worked" because it will depend on more "junk" mail coming in, and I haven't really received much of it (or much mail going to that junk folder - I only get a piece here or there every few days). However, what i have done for now is:
1) Open Mail
2) In the title bar, click on Mail, Preferences
3) Click on the "Junk Mail" icon
4) CHECK (select) the "Enable Junk mail filtering" box (this seems counterintuitive but there is a method to my madness; bear with me!)
5) Under "when junk mail arrives" select "perform custom actions (click advanced to configure)
6) Click the Advanced...button at the bottom of the box
7) A Junk mail "rule" will open. You can leave the description as "Junk"
8) A default rule will start "if message is junk mail."
9) Under "perform the following actions," if necessary click the drop-down menu and select "move message" and then use the drop down menu to the right to move the message to (your inbox, if that's what you want, or a different folder of your choice if desired).
You could add other rules such as "mark as junk" or to change the color if you desired, by clicking the plus sign to the right of the move message rule. Like I said, it won't be until I get my next junk mail until I know this works, but logically to me it would seem to have the same effect as turning off filtering (which as many other users on many other discussions of this topic have consistently said doesn't work).