WebKit only hides misspell underline for word including selection.start
I spent a little time looking at mispell underling today after noticing that FireFox's was strange. :) They're model is broken IMO (specifically regarding multi-word selects and right clicks), but ours is a little broken too.
1. Type "falskdj aldkjf adlfjk"
2. Notice as you select the 3 misspelled words that whenever the selection.start is inside a word, the misspell underline disappears.
I would argue we should only show misspell underlines when clicking on them will actually do something, thus hiding misspell underlines when selecting multiple words makes sense (sorta). The current behavior is a bad mix in-between hiding and not. Since if you select only one word, it won't show a underline (even though it should) and if you select 2 words, only the second will show an underline (even though right-clicking will not show you spelling suggestions).
This bug: Pick a behavior. Either always show all underlines, or don't show any. Don't "not show the first". :) I believe Word does not show underlines during multi-select. FireFox does. Someone will need to confirm that.