Here are a few things that irk me when I come across them.
Designers using the name John Doe Your users don't have perfectly short and sterile names. Use real and diverse names from different cultures. Show everyone that comes across your designs, as you sell them internally, about the diversity of your customers.
Unsolicited redesigns on Dribbble. Design is not done in a bubble. It is a collaboration between all the teams within a company. To present something without having gone through the collaboration, selling, and compromising that happens along the way is