Okay so this isn't the most mind-blowing news story you'll read today, but it's a useful new Pocket feature that's long been requested by users. To someone who hasn't used the app for a while, I must say I'm surprised to learn that highlighting wasn't already a feature. Not that it matters, now, as the latest update includes the ability to make passages of text a little bit yellow.
Version 18.104.22.168 was released yesterday and disabling Auto Play while listening is the only other notable improvement with this release. Highlighting is the headline though, which allows you to select and accentuate passages of text with a long-press shortcut. Anything you've highlighted will be visible in a list via a new 'Highlights' filter.
There's a small caveat, however, as Free tier subscribers will only be able to highlight three pieces of text per article. For Premium users this will be unlimited, of course. To check out the latest version you can update it via the Play Store or sideload it from APKMirror.