Good question, @DL! Which community site are you referring to?
The link that @VarunGrazitti posted is referencing Mobile V2, a product that we are not activating on customer sites any more.
That said, there are two possibilities of what you might be seeing depending on what you have activated. I am going to assume the 'predictive text' you are referring to is in one of your community search boxes.
If you are looking at our original mobile offering (this needs to be configured) you will not see suggestions from the community as you type. You would know if it is turned on because the experience is drastically different from desktop.
If mobile is not configured, you will see the desktop version of the site, and the search suggestions will still show up even though you are on a mobile device.
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