For anyone still looking at this querstion. This is for a hyperlink but you can modify it for just a plain underline:
Create a drawable (hyperlink_underline.xml):
<layer-list xmlns:android="http://schemas.android.com/apk/res/android">
<item android:top="-10dp"
android:left="-10dp"
android:right="-10dp">
<shape android:shape="rectangle">
<solid android:color="@android:color/transparent"/>
<stroke android:width="2dp"
android:color="#3498db"/>
</shape>
</item>
</layer-list>
Create a new style:
<style name="Hyperlink">
<item name="android:textColor">#3498db</item>
<item name="android:background">@drawable/hyperlink_underline</item>
</style>
Then use this style on your TextView:
<TextView
android:layout_height="wrap_content"
android:layout_width="wrap_content"
local:MvxBind="Text Id; Click ShowJobInfoCommand"
style="@style/HyperLink"/>