No, 1844 letter does not matter at all.
If you read the ICJ judgment , you will know what I mean.
5.3.5.
Conclusion
117.
In the light of the foregoing, the Court concludes that Malaysia
has established to the satisfaction of the Court that as of the
time when the British started their preparations for the
construction of the lighthouse on Pedra Branca/Pulau Batu Puteh in
1844, this island was under the sovereignty of the Sultan of
Johor.
(pg 36 )
So as in 1844, the judges has already ruled that PB
was still under the sovereignty of the Sultan of Johor, the context
of that 1844 letter does not matter, after all the judges have
already ruled in MY favour.
But in pg 49
163. In light of the above, the
Court will now consider the conduct of the Parties after
the construction of the lighthouse on Pedra Branca/Pulau
Batu Puteh to ascertain whether this provides a basis for
concluding that sovereignty over the island was passed from Johor
to the United Kingdom, Singapore’s predecessor.
So what were the conduct of both parties that came into
play after 1851 to 1980?
Well you could read the whole judgment on it, basically
from 1851 onward, SG has exercised a titre de souverain or "acts
consistent with being a Sovereign" on the 3 landmarks especially on
Pedra Branca and there was no protest from MY before 1979.
And especially MY thru 1953 letters and 11 official maps prior
to 1979 had admitted that Padra Branca belongs to SG, which
effectively ceded Pedra Branca to SG.
(Read from pg 74 on the final judgment on PB from para 273 to
277.)
So in conclusion, if anyone actually read the entire ICJ
Judgment, he will not make any stupid comment on the 1844 letter
regardless of the content, becos the judges has already ruled
that PB was still under the sovereignty of the Sultan of Johor in
1844.
The final judgment was based on the conduct of both parties on
PB after 1851, which in this case the judges has ruled that MY
effectively passed the sovereignty over the island from Johor to
Singapore!!!