I admit I did forget about that specific incident.
However, Dumbledore going cell to cell in Azkaban and Lord Voldemort attempting to subvert a prophecy predicting the end of the world in a fixed, controlled location seem like two very different things from a reader perspective.
It is also implied that Dumbledore did sense Harry's magic - at least on some level.
...the strongest had only as much magic left as a first-year child.
But he dismisses this because he is looking for a wizard strong enough to break into Azkaban and free Bellatrix Black. Lord Voldemort on the other hand, should be immediately and unconditionally suspicious of any and all magic he senses from Harry Potter.
the strongest had only as much magic left as a first-year child
That's Dumbledore reading Harry's mana level, not sensing whether Harry is casting spells.
This is a new thread to discuss Eliezer Yudkowsky’s Harry Potter and the Methods of Rationality and anything related to it. This thread is intended for discussing chapter 114, and also, as a special case due to the exceptionally close posting times, chapter 115.
There is a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author’s Notes. (This goes up to the notes for chapter 76, and is now not updating. The authors notes from chapter 77 onwards are on hpmor.com.)