A little bit off-topic but what is the difference between わ and は. And how does it come that it was so often mistaken with each other. Just curious :-)

I didn't notice this mistake until mattn pointed out it in twitter.

In Japanese, every Hiragana character (e.g. る, び, い, は) is basically pronounced independently of the context. わ and は are different characters so they are pronounced and written differently in general.

But a few exceptional rules exist. When は is a grammatical particle placed just after a subject word, it is pronounced as わ but must be written as は. This expcetional rule is one cause of the mistake.

Another cause comes from the word こんにちは. こんにちは is an ideomatic expression in Japanese used as a very (most?) common greeting messsage today. Noone knows what is the exact meaning of the word こんにちは, but it is believed that こんにちは was a shortened form of longer sentences like こんにちは良い天気ですね ("It is a nice day, isn't it?") which are not used in recent years. In the sentence こんにちは良い天気ですね, "こんにち" ("today" in English) is a subject word, so は should be pronounced as わ. It is obivious. No native Japanese speakers have a mistake. But in the shorter form こんにちは, it is no longer a complete sentence and は does not look like a grammatical particle.

I think these two are the reasons why we make such mistakes.

wow thank u so much for the explanation!