I'm not sure I understand. CommentExplorer only sends the currently selected file when selected with Up or Down key. If there is no comment, nothing is shown. If you are on the file you just added a comment to, press the arrow to go to a different file, then back. It should pop up the tool tip.
The reason I did it this way if I used the Windows Mouse Hover tooltip before. The font is small and hard to read. There's a lag time before the tooltip pops up. You have to register each file extension type to get it. This way I can use larger fonts. The response is nearly instantaneous. Any other way would hog system resources.
Also if you don't see any ToolTip and you know you commented the file, right click the Tray Icon and see if Arrow Tooltips has a Check next to it. If not, it won't show anything. Click it in the menu or double click the tray icon to toggle it.
This is in the Readme.txt file.
edit: It will only show the comment in Explorer when one file is selected using the Up or Down key. If you held down shift to select multiple files, you can comment them in a loop but to show the comment only select one file using Up or Down.