I am not sure if this problem is specific to OSX 10.7 Lion but in Scrivener the red underlines made by the Spellchecker are looking really buggy/ugly.
I compared with other applications and even if I am not totally pleased by how it looks overall it’s clear that under Scrivener they look uglier.
Scrivener:
TextEdit:
Although they certainly look odd in that screenshot, spelling underlines are entirely handled by OS X - there isn’t a line of code in Scrivener that touches this, so this must be down to the particular text scale, font or line spacing being used in this particular text. Certainly in all the texts I’ve used on Lion, spelling underlines look exactly the same in Scrivener as in other OS X text applications (as would be expected seeing as Scrivener does nothing with them).
Hope that makes sense.
All the best,
Keith
Zooming (vs. increasing the actual text size) will affect this–do you happen to have bumped up your editor to something above 100%?