I have posted the idea at windows phone user voice website as follow:
"Don't clear notification icon at the top bar when opening the action center, as long as there is notification in the action center the icon should keep showing at the top bar. Clear the icon only when all notifications cleared from the action center."
If you agree and want it to be real go and vote for it at this link:
Don't clear notification icon at the top bar – Feature Suggestions for Windows Phone
"Don't clear notification icon at the top bar when opening the action center, as long as there is notification in the action center the icon should keep showing at the top bar. Clear the icon only when all notifications cleared from the action center."
If you agree and want it to be real go and vote for it at this link:
Don't clear notification icon at the top bar – Feature Suggestions for Windows Phone