But not everything is used ironically. It's worth recording when they are.

I don't quite get what it's supposed to be mean though. Is 
"darling" referring to the adjective or the noun? If it's 
the adjective, then the 2nd sense is essentially just 
"lovely," but then I think the question is whether an 
"ironic sense" that is the very opposite of the "actual 
sense" is really necessary to include? Isn't it a bit like 
adding "(used ironically) stupid" to 頭がいい?

It was put in about 5 years ago by Kanji Haitani, a native speaker who was active for a while on the project. I knew him quite well - he was a retired professor who did a lot of translation. I'm sure he was correct.

source for sense 2?