Looking into definitions I think you can get away with using numbers as long as you just use it to mean the number (ie say 81 comments rather than eighty one comments) as using numbers like this doesn’t classify as text speak (please tell me if I’m wrong or have missed something, I’m basing this at least partly on what is considered acceptable in academic publications so i may have missed a site specific ruling).
I’m actively avoiding the other forms you mentioned though since i was made aware of the rule, for how often i used it, it’s not exactly hard adding on extra letters