I've occasionally left multiple kudos, because of the glitch, or accidentally reading logged out, or because I've switched my main pseud. It happens! I don't think anyone would get mad at it, necessarily.
From the author side of things, I'm used to assuming that 1 kudos=1 reader (who hopefully loved the fic). A lot of people do the same thing, if you've seen the posts about imagining your number of kudos as a crowd of that side. It's easy to assume that with logged in kudos because there are names attached, but with guest kudos, I just don't know. Do I have a dedicated audience of five readers who keep coming back, or an audience of twenty who stopped by once each time? if I get a sudden spike in guest kudos, did a bunch of people get to the fic at the same time, or was it one person over and over? Does my fic have broad popular appeal, or is it more of a cult classic? With guest kudos, I just don't know. Some people won't mind the ambiguity, but I know I end up wondering about it.
Personally I don't mind if people use guest kudos as an additional 'read this again, still love it!' feature, if they're going back to the fic every now and then. Honestly that feels kind of sweet to me, especially if you're doing it to older fic that might not get attention otherwise. I don't expect it though, and I don't think I'd want readers to feel that it's necessary, or standard practice. It's nice when it's occasional and unexpected.
I think I'd also feel a little uncomfortable in CotD's position. If the guest kudos start greatly outnumbering the logged in kudos, bookmarks, comments, etc on a fic, I might start wondering what it is about that fic that people don't want to interact with while named. Knowing that it was someone flooding the work with kudos might relieve that a little, but depending how significant it is, I'd still feel uncomfortable-- like I've been entered into some popularity contest I didn't mean to sign up for.