Every time I type if and press the space bar, Delphi completes it with if True then and a new empty line above.
Is there a way to remove this "autocomplete" feature or at least edit it to not create the new line?
That's called a live template, and you can edit the list of live templates in the template window, from the View menu.
Find the template you don't like, select it, and click the "remove template code" button.
Since the default location for the live code templates is C:\Program Files (x86)\Embarcadero\Studio\16.0\ObjRepos\en\Code_Templates (for XE8, similar for other editions), you will need to change the permissions on this directory (and its subdirectories) in order to edit or add live templates. Default permissions do not include write permission to this directory.