I think the problem he is seeing is that the property of "Halting" can
not be uniformly determined in Finite Time.
That is all that I can get from his statement of:
The idea of a universal halting test seems reasonable, but cannot be
formalised as a consistent specification.
There certainly CAN be defined formal test that define Halting, the
issue is that non-halting is defined by the non-existence of a number N
for the number of steps needed to reach a final state.
Some people just don't like the fact that it can be absolutely provable
what the answer is (and thus unknowable), even if we know from the
definition, that it must be one or the other.
This leads us to a great divide in logics. The classical branch accepts
that some truth is only established by infinite chains of connections,
and thus can not be proven with a finite proof, and thus is unknowable.
Others don't accept that, and require Truth to be only established by
Finite chains. The problem then is, such logic system need to greatly
limit the domain they attempt to cover, as otherwise you get into
endless chains of asking if a question can be asked, at which point you
need to ask if you can even ask about asking the questions. Only when
the domain is restricted in a way that the answer MUST be determinable
with finite work, can we break the cycle.
For instance, if we limit ourselves to Finite State Machines (which
could be Turing Machines with a fixed finite tape, or a classical
program in a computer with limited memory) then we can be sure that the
answer is determinable with a finite amount of work.