I've occasionally noticed, and commented on and downvoted lower quality, link-only answers, and you've definitely 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.