Here's a little something I cooked up for meme comments so you don't gotta squish...
1) Create a new image and set it's width to 1000
2) Fill it in with all black
3) Set the height to 1
4) Upload it on the Meme Generator, name it (I used "single black line") and check to make it available
5) From then on, you can use it from My Templates and just put the template you want under it with Add Image. The line doesn't even show.
Just tryin' to help.