(According to an earlier post on that thread, user @nullc is Gregory Maxwell, one of the core developers)
I haven't seen any evidence that they're testing anything— just the regular dust sweeping transactions that they've had going on continually.
Initially when MTGox suspended withdraws I was fairly confident that all would be fixed soon (and said so as much on Reddit)— their technical issues were simple, and with proper controls in place could not have resulted in especially large losses. I especially expected losses to be small considering that they were reported by users and not discovered by MTGox themselves.
Considering MTGox's subsequent behavior— the extended outage, talk of withdraw limits, etc, I'm no longer confident of anything.
Are there any news newer than this one, about the "MtGOX is testing" rumor?
Not that I have seen since - saw that yesterday - and I am pretty convinced from having read that thread it is indeed Greg Maxwell - he basically said they still haven't fixed it, and he wasn't at all convinced they were even close to doing it.