The link you provide is a good reference, although I can't recall a buyer ever asking me to check on his or her country's de minimus. I'd probably just tell them to call their nearest Customs Office, since I don't know that I'd want to be in the position of giving information to a buyer about their own importing limits, especially if it turned out to be wrong somehow.
By the way, most of us can happily forget about problems with U.S. buyers importing from us, as the limit has recently been raised to $800 US if I recall correctly. Of course, that's ignoring for the potential of the "Trump card".
In the end, it really is the buyer's responsibility to know his or her own country's import rules, not the seller's job to educate, cajole, or warn. This subject is admittedly a difficult one to navigate with the proper tone in a listing, i.e. to provide terms clear enough to transmit the basic facts, but not so harsh as to scare off buyers.
Although I do believe eBay's one-line reminder is probably sufficient, and I'm not convinced most buyers read very far down a listing anyway, I still include my own wording about customs and duties, albeit in somewhat softer terms than the text you've posted. The "Learn the rules before you bid or buy" statement comes across as unnecessarily aggressive. While I understand your reasoning as a seller, if I read that statement as a buyer I might turn away before looking further.
To be honest, I would also delete everything after "Cross-border Shopping?" in your title line. The rest of that line, as much as it may be an accurate statement, sounds blunt and very unfriendly put in the imperative, as if you regard your buyers as uninformed trouble-makers. The phrase "KNOW YOUR LIMITS" is really not something you want to appear to be shouting at buyers. At least that's how I'd receive it as a buyer.
The whole issue of buyer complaints over unexpected taxes or duties has become far less meaningful anyway, now that eBay feedback no longer counts for much, and now that eBay CS can look into a seller's messages to a buyer if the issue does arise.
I wouldn't put the link itself into a listing (I realize you weren't suggesting this) because eBay discourages links relating to listing terms unless they are single links (in other words, dead-end links) without links to other pages outside eBay:
"You can include a single link to a page that gives additional detail about the terms and conditions of the sale. However, the page you link to can't include links to web pages outside of eBay, and the information on that linked page can't contradict the information in your listing."
(From the policy): http://pages.ebay.ca/help/policies/listing-links.html
However I think it's enough to simply direct buyers to contact their country's customs office for information on what their permitted import levels are.
Here, for what it's worth, is the text I use, although I've been considering removing it completely, since almost all of my sales are to the U.S. which (as noted above) now has a very, very generous de minimus. By the way, anyone who wants to use this wording is welcome to do so (yes, I know, insurance is for us sellers, but I needed a "soft" rationale for not making under-declarations of value:
"U.S. and international buyers: We are located in Canada. Import duties, taxes and charges by your own country are not included in the item price or shipping charges quoted in this listing. Please check with your country's customs office to confirm what these costs will be before buying. These charges are usually collected by your country's customs/postal service when you pick up the item -- please don't confuse them with additional shipping charges by the seller.
Please do not ask us to falsify customs values or mark an item as "gift". It is illegal to do so. In any case we must declare the actual price an item was sold for in order to validate your insurance coverage."
