I would like to see the codes of emoticons in tooltips when I hover my mouse on them in conversation windows' "Received and sent messages" section. I find the tooltips very useful while reading HTML chat logs of Plus! and would like to have them in conversation windows themselves because some of my friends assign words as the shortcuts of their custom emoticons and I have to right click on those emoticons and click "Add" to see the assigned shortcut for them and understand what my contacts  wrote there. I think most of the people would like this feature and this feature would be as useful as the "Enhance the text copied to clipboard" option of Plus!. Note: I don't want to disable emoticons in case you would suggest it to me.

As you know when you hover "Received and sent messages" section, Messenger's own tooltip appears and reads "Received and sent messages" so the tooltips of emoticons can be shown when we hold Ctrl key pressed while hovering on them if possible.

I'm going to say its most likely NOT possible, because the whole conversation area already has a tooltip (at least it does for me in 8.1)
"Messages that you've sent and received"