Pressing Ctrl+Home bring you to the top-left of the message, not the beginning of it; pressing Ctrl+End bring you to the bottom-right of the message, not the end of it. That means that if your message direction RTL instead of LTR, Ctrl+Home and Ctrl+End do not bring you to the start and the end of the message, respectively.
Problem code is at http://lxr.mozilla.org/seamonkey/source/layout/html/base/src/nsPresShell.cpp#324 6 it does not take BiDi into account. In fact, it is poor design. Instead of seeking to some desired set of (x,y) coordinates - and then using the click handler, aarrggh!! - the code should find the first element, in logical element order, within the frame, and position the cursor before it. I think I'll open a separate bug.
IIRC, fixing 263309 automatically makes this go away. Someone please check this with a trunk build from after the checking for 263309.
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