Instead of allowing users to converse within its official Facebook app, the company now forces users to install its standalone messaging app in order to converse with friends.
However, with a simple workaround, iOS users can re-enable the Messages tab in the official Facebook app and forgo the need to install Facebook Messenger.
The only catch it seems is that this isn't a permanent fix. I used Messages within the Facebook app over a 24 hour period and at one point it reverted back to the "Install Messenger" prompt. Thankfully, simply performing the workaround again removed the prompt.
Here's what you need to do:
Step 1: Select the Messages tab in the official Facebook app. This will present you with a new page, prompting you to install the Messenger app.
Step 2: Tap the install button. The App Store will launch to the Messenger page, were you can begin the download. As soon as you begin downloading the app, delete it. That's right. Don't even let the app install.
Step 3: Go back into the Facebook app, tap on Messages and do the happy dance. I know this sounds like a lot of work, but if you're set against being forced to use Facebook's Messenger app, this is a solid option. You can always check out Rick Broida's suggestions for skipping out on the Messenger app.
I can't take credit for this working, as I discovered it on Twitter.