In Revit, texts can only snap to other texts. It's strange, but it's Revit way ;-)
If you want to align a text accurately on a specific point, select your text, then click on the Group tool . The group insertion point comes at the center of the text box. Now, use the Move tool to put your text on the target point. You can snap to the group insertion point () for the start point.
Finally, delete the group.