In the interests of quoting the full context rather than just a few words, here's what he said in full:
"Dear The Great Developer of "Dash.app".
I do not ask you anymore.
I do not say anything about your icon.
It's a waste of time.
But I am vindictive.
Conversely, I inspired from your icon.
This is the way of my protest.
This time, you do not plagiarize this my icon, please.
Sayonara ăăăȘă."
It seems the designer is Japanese, so there might be a language/cultural barrier too, but for what it's worth I think I would feel insulted by the Dash developer's reactions too!
"Dear The Great Developer of "Dash.app".
I do not ask you anymore. I do not say anything about your icon. It's a waste of time. But I am vindictive. Conversely, I inspired from your icon. This is the way of my protest. This time, you do not plagiarize this my icon, please.
Sayonara ăăăȘă."
It seems the designer is Japanese, so there might be a language/cultural barrier too, but for what it's worth I think I would feel insulted by the Dash developer's reactions too!