0 rude and not considering other people's feelings:
1 not caring enough about other people’s feelings; not polite:
I felt it was discourteous of him to leave immediately after his talk.
Thanking someone in this manner may sound discourteous.
He may even, perhaps unintentionally, seem discourteous in the authorial relationship.
The second is more discourteous.
Was not that reply singularly uninformative and also a little discourteous?
I thought that discourteous references to leaders of foreign countries was something to be deprecated.
It is a singularly discourteous proceeding, against which an immediate protest should be made.
I hope that this serious incidence of discourteous, incompetent and inconsiderate behaviour will not be repeated.
I hope that it will not sound discourteous.