Mumsnet website autolinkifies and adds the mumsnet referral to Amazon links, so Amazon links are clearly recognised and treated specially. But they also break for my usual links which are smile.amazon. Using the Smile version donates half a percent to the charity of your choice, so should be encouraged. Example:
amazon.co.uk/s?k=crucial+bx500]]
That started as smile,amazon,co,uk/s?k=crucial+bx500 except with dots not commas of course.