The rule of thumb to distinguish the two phenomena is as follows: when an expression refers to another linguistic expression or a piece of discourse, it is discourse deictic.
Spatial modulations can perform various functions including indicating person or number; providing deictic, locative, or temporal information; or indicating grammatical relationships.
The former is used as if the words being used were those of another, which are therefore pivoted to a deictic center different from the speech situation of the report.
