It happens to me often on the default theme, using Firefox (but I'm not entirely sure it happens across all my systems and Firefox setups). If I'm entering a long message (including PMs), then cursor back slightly and hit one of the formatting buttons, it'll jump to the top of the message.
I've got the Text Formatting Toolbar extension installed in FF, which helps (it doesn't jump if I enter the formatting codes that way (or manually, of course
)), but that's just a workaround.
Still alive, but failing miserably at dodging Real Life.
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