Our team just upgraded to the latest version of phab, and I now find that I can't at-a-glance spot the difference between open and closed tickets as easily as I did previously.
Currently, the only difference between open and closed tickets is the rendering of the ticket number:
Previously (I'm sorry I don't have an exact screenshot) the closed tickets were much more obviously grayed-out. Something like this:
The latter was much more useful as my eyes were drawn immediately to the open tickets but I could still note the closed tickets if needed.
In case relevant, I'm running on an up-to-date version of Chrome on OS X. I will follow up with a comment indicating which commit/version of phab we're running. Please let me know if there's any more information I can provide.
I'd also be happy to submit a patch if that's of interest.