x:Bind需要代码隐藏。（请参阅此处）
因此，多亏了MainWindow.xaml.cs，这才得以实现：

<Window
    x:Class="Bindings.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:local="using:Bindings"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    mc:Ignorable="d">
    <Grid>
        <Grid.Resources>
            <Style
                x:Key="CustomButtonStyle"
                TargetType="Button">
                <Style.Setters>
                    <Setter Property="Template">
                        <Setter.Value>
                            <ControlTemplate TargetType="Button">
                                <Border
                                    BorderBrush="{x:Bind BorderBrush, Mode=OneWay}"
                                    BorderThickness="{x:Bind BorderThickness, Mode=OneWay}">
                                    <ContentControl Content="{x:Bind Content, Mode=OneWay}" />
                                </Border>
                            </ControlTemplate>
                        </Setter.Value>
                    </Setter>
                </Style.Setters>
            </Style>
        </Grid.Resources>
        <Button
            BorderBrush="SkyBlue"
            BorderThickness="1"
            Content="Custom Button"
            Style="{StaticResource CustomButtonStyle}" />
    </Grid>
</Window>

对于自定义（模板化）控件，我会选择：

Text="{TemplateBinding Text}"

或

Text="{Binding RelativeSource={RelativeSource Mode=TemplatedParent}, Path=Text, Mode=TwoWay, UpdateSourceTrigger=PropertyChanged}"

用于双向绑定。
如果您想在ControlTemplate中执行x:Bind，这个answer可能会有所帮助。