Ask.com does not have a messaging feature, but if you would like to carry on a short conversation with someone, you're welcome to do so in the comments section under an answer. As long as your comments are within the Community Guidelines then you're fine :)
There isn't a feature on this app that allows you to do so. You should recommend chatting in the feedback section of the app. Select "more" on the bottom right hand corner of the screen. The feedback will be there.