The Recipe: Crafter’s Mark of the Chained Isle can be purchased from Archivist Roh-Suir in Korthia. There’s no indicator of having learned the recipe nor does the recipe disappear from the vendor’s choices (the later being the method used for other items sold by this vendor)… so the item is prone to be purchased more than one by a player only for them to try to learn it, fail, and have to sell it back to the vendor. Please make this work like the other items.
I think the item may remain to be available in the case that you change your professions and need to repurchase it, but I think it would definitely be helpful if it said it’s already learned if you already know it on that current profession, and the purchasing behavior needs to be adjusted in some manner.
I included this again as part of a larger meta bug report regarding the crafter’s marks on 2021-08-05: Crafter’s Marks and Missives aren’t working for crafting multiple items. This new report summarizes multiple related reports and links back to the originals, including this one.