How are you adding a comment? Because I am able to see the comment on the view after the edit also. Here is how I am doing
Right click on view -> View Information -> Write comment in comment area and hit OK. Afterwards if I go again, I can still see and edit the comment.
The only difference is I am connected to Enterprise edition instead of XE. I hope XE is not an issue.
it doesn't appear afterwards if I try to edit it using the GUI.
Did you refresh the object tree in the GUI? Just because you execute SQL doesn't mean the GUI is going to know anything about that change in the dictionary.