This way of representation is used with parenthetic sentence parts or, as the case may be, embedded clauses] that do not violate the sentence structure.
However, some constructions separated by commas are not regarded as parenthesis, which, of course, concerns embedded clauses, attributes separated by commas that are considered to be "free" attributes and get afun Atr (e.g. děti, umístěné v ústavu, něco sebraly children, placed in the assylum, stole something), and complementation expressed by a transgressive (see Complement expressed by a transgressive). The afuns with the suffix _Pa is used in these cases only if the given construction is separated by certain graphic symbols.
A special situation obtains if parenthesis is one of the members of coordination, which as a whole is not a parenthesis. In such a case the suffix _Pa is not used because there is no place to suspend it.