I tried the solution you suggest, but even clearing all sites from 'site settings' and unchecking the autosync option has not solved my problem. The root of the issue for me is clearly the predicitive text, which is a function I want for texting and writing in general, but don't want since it keeps remembering names of websites I've visited in incognito mode.--------------------------
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Open the incognito browser, click the top little menu on the screen for the Internet settings. Scroll down Click "settings", scroll down click "site settings" at the top you should see "all sites". Click the site you want to clear. Hope this helps! I was super frustrated for a long time over this too. I have the galaxy s5.