I guess if you use the Latin form of a plural you do however have to take care that it is actually correct as if not you're going to look a bit of a pillock.
For example, although many singulars ending in "us" take a plural form ending in "i", some (4th declension) don't. For example I think "virus" and "prospectus" also take "us" in the Latin plural and that would sound odd in English.
Oh, I've just seen that criteria thread. In a bit of pain now. I see people getting it wrong a lot, but not being all righteous about it. I daresay we'll come to the point where the plural becomes the accepted singular, but we're not there yet.
I like Anglicised plurals too. 'Octopodes' etc is interesting from an etymological point of view but I'm never going to actually say that. It reduces the chances of getting something 'wrong' too. Good point about 'crisises' though! I can't bring myself to be annoyed by 'panini/paninis' in English, either.
Having just jumped on someone else for using 'criteria' as a singular, I actually agree with you!
Am perfectly happy with forums. And octopuses. After all, we say 'cinemas' not 'kinemata' (or whatever)! OTOH I have a day full of crises not crisises. And what about more modern borrowings such as 'panini'?
It's all about usage really, rules are more descriptive than prescriptive.
Want to post in AIBU really, but it's a bit specialist and probably belongs over here. Am I getting unnecessarily irritated by the use of 'fora' as a plural for 'forums'? Sure, forum is a Latin word, but I don't believe it was used in the sense of an internet discussion board back in Julius Caesar's day. It has been adopted as a modern English word and should therefore have a modern regular English plural for the sake of clarity.