An attempt to see a Differential revision [like <Phabricator instance URL>/D6] results in the following error:
UNRECOVERABLE FATAL ERROR <<<
Maximum function nesting level of '100' reached, aborting!
┻━┻ ︵ ¯\_(ツ)_/¯ ︵ ┻━┻
P.S. 1) Unfortunately, I cannot provide reproduction steps at this time - perhaps, the error is spurious and caused by a combination of factors, but I hope the error message is self-explanatory; 2) I'm not sure where to obtain the Phabricator's version info, but, if it helps, the system it is running on is Ubuntu 14.04, or, more specifically the following:
Linux ABCDE 3.19.0-33-generic #38~14.04.1-Ubuntu SMP Fri Nov 6 18:17:28 UTC 2015 x86_64 x86_64 x86_64 GNU/Linux