This is something I’ve struggled with — some people are just brisk, and they don’t intend to come off rudely. It can also be a language barrier. I always give them the benefit of the doubt (especially if there are other indicators that they are not being rude, such as leaving a long and detailed response that took them some time). Communication via text will always be open to interpretation. Personally, I don’t hesitate to throw in an emoji if I want someone to know I’m being friendly — especially if I have to give a long constructive criticism of a patch to a new contributor or something.