[Ripplinger]

I think it will revert back to 1 if you open a book that's already been opened as GeoffR explained above. Or if you touch the slider for the line spacing again, then it most definitely reverts back to 1. But I just plugged my reader in again after deleting and reloading all my books and checking several books on it last night night, and the Kobo eReader.conf file remains at .90.

Edit: After I synced it, it did indeed revert back to 1 again though, and books that were showing 25 lines last night are now back to a max of 21 lines. It seems pretty touchy what will revert it back. At least I'm assuming the sync is what caused it to revert.

Edit 2: I removed all books again, loaded them again, made sure line height was back to .90, and it is working again. The odd thing is though what used to be 25 lines per page is now 23 lines per page with the same settings. It's still better than it was, but just seems quirky. The minimum of 1 isn't that bad, not as bad as it was with older firmware at least, so it's livable if it's something that just won't remain as set through syncing.

Actually, it seems to revert back to 1 no matter what. When I reopened a book that was showing 23 lines per page, it was back to 21 lines per page. When I checked the .conf file, it was oddly still at .90. So it doesn't seem to be a reliable fix this way anymore.