I agree that the solve blocks look quite ugly in Prime but I don't think that there is away to change this.
I am not sure which "documentation" you are referring to. To the best of my knowledge a documentation which would deserve that name does not exist - just the help pages. In real Mathcad we had a good documentation (up to MC14 even in printed form) and up to MC11 it also included a concise and large reference section.
What we see in the help pages of Prime are not solve blocks, but just the regions inside and the border you see there around them seems not to be original border of the Prime solve block. I guess this was done to be able to use them for all language versions of the help pages.
On contrary to the help in real Mathcad the help pages are not live, working Mathcad worksheets but rather only HTML pages where some expression were underlaid with the code of Prime regions which you can copy to your worksheet using the offered "Copy Expression" button.
If you copy as solve block from the help pages to a live worksheet that way, you again have the ugly display.
---> 
For presentation you might have to resort to some trickery, I fear. You may hide the original solve block in a collapsed region and paste an edited picture of the block without the labels below. Of course it would not be a live worksheet now anymore and for me this sure would not be worth the effort.