clicking on text to place cursor, causes unwanted highlighting of text.

Hello,

I’ve upgraded to 5.3.0.3 from 5.2 and there is a new feature that is tearing my hair out!
When I click on a line of text, something between a word, several words, or a whole sentence is highlighted.

I want to place the curser somewhere to do some some kind of editing, but this feature assumes I want to automatically delete the highlighted text. This feature is causing me to loose sentences to paragraphs!

I absolutely hate this feature with an explicative passion! How do I turn it off!