Just to clarify. I mentioned .fontcs as a flag to indicate when this bug happened. When active font is Aharoni, the sample characters for the David font shows the Hebrew symbols because there's a correlation of them both sharing the same 147 .fontcs, but active font Consolas doesn't show David having Hebrew symbols because their .fontcs values are different.

As for the sample text being chosen by Windows itself, I can see that notepad also shows AaBbXxYy, though it does not have the bug I mentioned. In notepad when the active font is Consolas, unlike mIRC, David does show the Hebrew symbols and Wingdings does show the waterdrop envelope etc symbols.