I've occationally noticed, and commented on and downvoted lower quality, link only answers, and you've definately got a *lot* of rep - and well, If I thought one of your answers wasn't good, I'd consider downvoting and commenting. Not everyone might do the latter. In your case these would be link only answers, with some older, bountied questions if I recall correctly.

To put it mildly, there isn't really a problem IMO

The *proper* way to deal with this, in my opinion is rather than protecting older questions from downvotes, is for answers to be *updated* as you notice they are downvoted. This has a few advantages - it gets better visibility for the *question*, and if your answer is fantastic, people would upvote it anyway.