Can't compare old version with new version of post or page

I was trying to copy an old version from several versions ago with the current version using WinMerge but I can’t copy one side without it selecting the other side because each line is inside a td tag rather than each side being in its own div in two columns. Everything I’ve ever learned about displaying things in HTML says to put layout in divs and data in tables (and this is not data and it’s being done wrong even if it were), so can we get this changed so one side is copyable? I don’t know how to compare one version from another unless they’re right next to each other, and I don’t want to overwrite the current version and add another version to history which can get confusing.