The humour was in the irony of showing an earlier example of macrons/breves than a 19th century Gradus was an 18th century Gradus. Same book (basically), but different century.
Humor is not irony. There can be irony without humour; when sharply critical, it's called sarcasm. What the rest of us understand as humour is a light-hearted remark added beside the point, signalled by overt signs that make it clear that it's not intentended to address the point directly, and whose unexpected nature is meant to divert and remind the interolocutors that the person isn't taking the matter overly seriously, or doesn't think it worth spending too much time on.
There is nothing of that nature whatsoever in your words. There's no light-heartedness or beside-the-pointness, and no indications of a humorous nature. You're addressing what I said directly, and correcting my dates because you didn't understand me right - that the system
spread in the 19th century, not that it
appeared in the 19th century. In your reply you provide
proof (links) that they did appear before the 19th century, and you mention an entirely different book (Forcellini) which has nothing to do with any supposed "same book, different century" irony, and makes it absolutely clear that what you're doing is absolutely earnestly trying to demonstrate that my dating was incorrect.
The real irony is in the following:
You have to grant craziness is the normal interpretation of that smiley... I and most everyone would normally use it when calling another person crazy / nonsensical.
Smileys are the basic way to signal light-heartedness and humour in internet communication. You were in fact taking the matter so seriously that you've managed to interpret a smiley as me "calling another person crazy / nonsensical". What my smiley tried to convey is the humorousness of the way you misunderstood me, namely how confusing the result is when you put together what I say and what you say. The smiley stands for "confusing" and is followed directly by "xD", a smiley meaning "haha, funny". It relates to the humorousness of the situation and is not an attack against your person. Not only did you miss the humour entirely and thought I was was calling you crazy, you're trying to convince me that that it's me who missed your "humour". There is a very obvious explanation to this whole situation, that I'm starting to suspect you're unaware of, and that I will provide in a private message.