Note: AFS treatment reports the BOOK VALUE not MARKET VALUE
You can read this: https://corporatefinanceinstitute.com/resources/accounting/a... to understand AFS vs MTM treatment.
Losses are reported, definitely not clearly. Losses are hidden under "Other Comprehensive Income." If you want to be transparent about it, then it should show up in the Profit and Loss. You'd choose MTM accounting treatment. Not choosing MTM accounting treatment is literally hiding the losses into a vague bucket of income.
The idea that this was somehow hidden needs to die. People knew they were vulnerable to a run not due to some shady rumor Network, but because they reported exactly what they were doing plain as day.
They were making low but positive interest profit on those assets. They simply locked up too much money in a long-term investment to withstand a coordinated Bank Run. This was a real mistake, but it is not at all about secret accounting.
Anyone who can do simple arithmetic could determine that they were at risk in a bank run from their published documents. Most of the world simply did not care because they did not think the Run would happen
This misinformation needs to stop.