In mathematics, it is not uncommon to attach emotionally charged adjectives to theorems. For example, nobody would raise an eyebrow at phrases such as "beautiful theorem". It goes without saying that such praise is only appropriate when truthful: it would be bad form to call a result "exciting" simply because you happend to be proving it's generalisation. Also, modesty requires that you should never say such things about your own work.
I personally find such language quite helpful. It is useful to know if a given result is something to get excited about or not. Sometimes, resuts speak for themselves, but this is not always the case (and there isn't always space to explain the reasons properly, especially if you just mention a result to provide context).
I'm not sure to what extent these rules extend to other fields.