Also, what kind of danger are we talking here? I consider mutation dangerous. Danger could also mean it has side effects or that it can raise an error.

I wouldn't call it inconsistent but I would call it arbitrary.

I would rather just name the method "#{base_method}_#{why_its_dangerous}". For example take ActiveRecord::Base#save and #save!

#save mutates and I would consider that dangerous. #save! can raise an error. I would rather name #save! as #save_or_raise_if_invalid. I know it doesn't look as pretty and takes longer to type but I really don't care. Then again, I'm not a big fan of exceptions so I would never call it.