The Wolf
First of all I dont know you personally but you have this manner of putting yourself down and saying negative things about yourself which really makes me uncomfortable. I dont think its proper for you to put yourself down whether you really have a low self image or just for fun because some people will take it seriously and if you really feel this way about yourself you need to speak to a professional. If you are doing it for humor, its not funny and insensitive to those who themselves struggle or have struggled with self image issues.
Now on to your post.
I think you have made a very valid point and I have seen this done elsewhere. You are 100% correct that it is wrong and disrespectful. It shows I dont care what you have to say r that you are boring…Its especially rude when the person is right in the line of sight of the Rav or speaker…If the Rav is speaking for a long time and goes on and on and is really very boring, I cant judge someone who is sitting in the back and knows for a fact that he cant be seen by the Rav for taking out a sefer and finishing maavir sedrah or whatever.