Thanks for reaching out in the Community! I can definitely see why this would be an issue. We are tracking responses on this issue and I have added your feedback as well.
Please let us know if we can do anything else.
I wanted to provide a little more information on what appears to be happening in your emails. You are using our Legacy Editor which is prone to latching on to styles and formatting that may have been present in the source that the text was copied from. This results in there occasionally being some buildups in the HTML code of the block that can cause some strange instances, such as the extra line break that you are experiencing. We do encourage migration to the Third Generation Editor since we see fewer instances of text changing like this, but also for its compatibility with mobile devices. Alternatively, though, I would suggest deleting old blocks and placing new ones in before adding your copy as well as pasting the text in to a basic text editor to clear background styles before copying from that text editor to paste into the block.