To reproduce, edit a page in Visual editor, create a table, select some cells, and right-click them.
- Result in Firefox: A "Copy" command is shown in the context menu. Clicking it copies the cells to the clipboard, and they can be pasted.
- Result in Chrome: There is no "Copy" command in the context menu.
The keyboard shortcut Ctrl-C/Cmd-C works as expected in both browsers, so the copying action is definitely possible, but in Google Chrome it is not accessible to people who do it using right-clicking. I practically always use the keyboard shortcuts, but I see a lot of people who prefer copying using right-clicking, as inefficient as it may sound, so this should be possible.