As both a Firefox and Pocket user this confuses me. What in particular does Pocket do that would have been hard to do? They already have Sync that moves extens

As both a Firefox and Pocket user this confuses me. What in particular does Pocket do that would have been hard to do? They already have Sync that moves extensions, bookmarks and settings around between browsers. The reading mode in Pocket is far from perfect. I use to maintain a FF extension that did something similar and it wasn't much more that a CSS file.