I experience this problem as well - whenever I have selected a file within a PathFinder window. But I recently noticed that the feature works fine (click to select, then click again to edit filename) works fine for a file on the (PathFinder) desktop.
Thanks for the tip about using the keypad Enter key.
So guys, I'm just wondering, I see this thread gets closed and then re-opened, then closed, then re-opened. What is the status of this bug? It seems enough people are experiencing this that it has not been completely resolved. I've searched through numerous posts here and don't find a solution to the "slow double-click to rename", only work arounds. I just updated to version 8.3.8 (on Mac OS 10.13.6), and still cannot use the slow double-click to do a file rename, which is the normal Finder option (which does work, BTW). Would love to know if this is being worked on...or not.
Just responding to the latest post, although I had posted about this before Nov 15, 2018. I still cannot click-to-rename WHEN I am in COLUMNS view. However, I have found that when I am in ICON view or LIST view (as well as when I am on the desktop), I have no problem clicking-to-rename.
My default (and preferred) view is COLUMNS. So, when I want to rename a file, I quickly switch to LIST view, rename the file, and return to COLUMNS view. Clearly this is clunky, but it is not as frustrating as repeatedly trying to slowly double-click or change to Info panel to rename.
Another user with the same problem, which has been ongoing for a VERY long time now. Thanks to mhwill for pointing out this issue only occurs in column view (my default usage mode). It does indeed work perfectly in List and Icon view. Like others, I added Rename to my contextual menu, but all of these work-arounds are simply annoying for what is essentially a productivity tool. And I have found another related bug that results from using the Rename contextual menu: when I create a new folder, I give it a name in the drop-down menu and hit OK. The drop-down closes, the folder is created and the drop-down then opens again, but this time as the Rename drop-down, containing the text I last typed in the Rename field. This happens whether I hit OK or Cancel on the drop-down to name the new folder.
I'm using PathFinder 8.3.9 on Sierra 10.12.6