There's no way to turn it off, and you're actually doing two different things.
In the first case, you undoubtedly selected only the text of the action, not the entire row. When you copy and paste, you get exactly what you expect.
In the second case, to do the selection, you are actually selecting multiple rows in their entirety, and when you copy and paste an entire row, OmniFocus puts a link to the row in the clipboard, with the display name of the link being the text of the action. If you copy and paste multiple rows, you get a bunch of links, as you discovered.
If you want to copy just the text of multiple rows, you could use an Applescript like the one included here.
tell application "OmniFocus"
tell front document
tell (first document window whose index is 1)
set theSelectedItems to selected trees of content
set indx to count items of theSelectedItems
if indx is 0 then
display dialog "Please select one or more rows and try again"
set clipboardText to ""
repeat while indx > 0
set selectedItem to value of item indx of theSelectedItems
set clipboardText to name of selectedItem & return & clipboardText
set indx to indx - 1
set the clipboard to clipboardText