Also you can confirm that trailing empty line is definitely a bug by setting the line limit to 3 and then pasting for example
"hello
a"
mIRC will ask if you wish to paste 3 lines. Not 2 and if you select that you wish to do this, mIRC says only 2 lines and ignores the empty line. By your logic, mIRC shouldn't warn me about pasting that because it's only 2 lines getting the /say treatment.
Just a quick note on this part... mIRC does not go through and parse your entire pasted text to find empty lines. This was mentioned earlier either in this thread or the other one. So any empty lines in the middle will still be treated as a line when pasting regardless of whether or not it pastes it. It certainly could check for that, but that would be processing more information when you paste. It's very easy t do a count on new line characters to determine how many lines there are and it's very easy to ignore the last empty line(s) in that count. It takes more work for the software to really parse through the text and determine how many lines there are after removing blank lines. It would probably be worth it to do that, though. If it's not going to send to the server, why count it?
Personally, I think the proper way to handle the line count when using the confirmation is that it counts all lines ending in a new line character and ignores any that are not ending in a new line character. After all, if the last line doesn't end in a new line character, then it's not being sent to the server, so should not be counted. The purpose of the confirmation isn't to prevent you from pasting text into your edit box by accident, but to keep you from sending it to the server by accident. If it's not being sent, there's no reason to count it. That really isn't a bug, but just something that was probably not considered when it was added.
And, so you are aware, telling people why something works the way it does or why something isn't a good idea does not make someone a "troll". It's also not a bad thing for people to do this. There has to be a discussion of all sides (pros and cons) for a developer to decide what is worth doing and what is not. If no one was allowed to disagree, then you'd have a ton of suggestions where most of them are things that a lot of people wouldn't want. If the developer doesn't know that, then the software can end up becoming garbage really quickly. You may not like people shooting down your ideas or telling you why something is the way it is, but that's necessary for good development (seeing all sides). It also lets you learn about the software so you can make better and more informed suggestions... assuming you care to learn from what people say. Finally, name calling is never a good way to get anyone to listen to what you say. Keep doing it and no one will care about your suggestions even if they are good suggestions and then you're just wasting time typing for nothing.