The game will display a warning prompt before attempting to remove or unwield a fragile item.
Fragile artefacts tend to have more powerful properties than similar artefacts of the same type, but their obvious downside is their inability to swap them out for other items. This makes them a poor choice for ranged weapons and some melee weapons, but a potential option for some jewellery and armours, depending on the other properties or egos that generate alongside it.
While this property is fairly uncommon, it is a good practice to identify any desirable unknown artefact before equipping it; once a fragile item is removed, it is unrecoverable.
Fragile was added in 0.18.