I am afraid you are the one who misunderstood me. What you mean is thoroughly clear to me from the beginning because I had read your explanation titled "Adding another comment" before I made the first comment, of course. And still, I'd say again that we would more often say like No.6 rather than No.4 or No.5 even as additional comments for the reason I have already mentioned.／It might be natural for native speakers of English to say that way, which is absolutely not here in Japan. You could write in a message like No.4 or No.5 because it is grammatically correct, but it would at least not sound like a native speaker of Japanese because most of us actually don't say that way. Nothing more, nothing less. Anyway, I suppose non-native speakers of some language don't need to speak it as native speakers do. ／In other words, we are not people who say "Have a nice day", at least as often as you do. It is just like you don't say "お疲れ様" as we do. There are really big cultural differences between Western countries and Japan in the Far East, I'd say.

Hi Ueda-san, thank you for reading and leaving a comment. To be clear, what I mean is that numbers 4 and 5 are additional comments you can write in a message.

I don't mean to suggest that 素敵な一日を means "happy birthday", but that you can write (for example) お誕生日おめでとう！素敵な一日を when wishing someone happy birthday.

Likewise, of course 素晴らしい１年になりますように does not mean "happy birthday", but you can write お誕生日おめでとうございます。素晴らしい１年になりますように。

I hope that is clearer?

I am a native speaker of Japanese. Honestly, I have hardly ever heard someone say No.4 or No.5 here in Japan. They might be quite good translations for those English phrases such as "Happy birthday! Have fun :) " and "Happy birthday! Have a great day" , though most Japanese would not say that way. ／It is probably because we are not so interested in how we just celebrate our birthdays as in how we spend a good time for another year, which would be much more difficult.