There is no way for a user to change the caption justification from center to left (well… I should say, at least I don't know how you do it), but the very dark transparent OSD (on-screen display) background can be modified via the skin main.XML file. You did not specify which skin you are using (modern cards? noire?). Most skins simply use the default OSD background image included with every MC install.
Regardless of which skin you are using however, you can force the skin to use a custom image with a lighter transparency by adding the following subsection to the main.XML file for the skin you are using:
OSD>
<Data InternalMarginLeft="16" InternalMarginRight="16" InternalMarginTop="5" InternalMarginBottom="5" />
<Entry Name="Background" Bitmap="OSD_Frame-1.png" NumberImages="1" Margins="20,20,20,20" />
</OSD>
The 1st pic shows the OSD with a light transparency (corresponding to the attached OSD_Frame–1.png file), and the 2nd pic shows what it looks like with the OSD background disabled completely. To accomplish that, simply delete any letter within the quotes of the
Bitmap entry above... or delete the entire filename altogether - but be sure to leave the quotes ("") or the skin will break, or possibly just revert to the default dark background again (I can't remember which). If you don't like either option shown in the pictures below, you can always create your own custom image and replace the one I included.
After all that, you're gonna want to save this skin to a new name, otherwise it will get overwritten every time you do an MC update, and you will have to repeat all the steps above again. It's not as simple as just making a new skin folder please, though you will need to do that as well. Read Post #4 on this thread:
https://yabb.jriver.com/interact/index.php/topic,131307.msg936939.html#msg936939 for additional information how to go about doing it correctly.
Hope this solves your problem… At least in part.