Get Filtered Data Range in a Table Purpose:
Given a Worksheet Table (ListObject) that may, or may not, have a filter currently applied to it, return a range consisting only of the filtered data.



Method:
Loop through each row in the table.
If row is visible, add it to a filteredRange via Union().
Return filteredRange.



Specific Areas of Interest:
Is the function name sufficiently intuitive?
Is there an easier way to achieve the desired results?
Are there edge cases I haven't accounted for?



Function:

Public Function GetFilteredTableRange(ByRef targetTable As ListObject, Optional ByVal includeHeaders As Boolean = False)
    '/ given a table, return a range object that contains only those rows which are visible
    '/ Do this by looping through tableRows, adding all visible rows to a unionRange

    Dim allDataRange As Range
    Set allDataRange = targetTable.DataBodyRange

    Dim filteredRange As Range
    Dim rowRange As Range

    If includeHeaders Then
        Set rowRange = targetTable.HeaderRowRange
        Set filteredRange = rowRange
    End If

    For Each rowRange In allDataRange.Rows()
        If rowRange.EntireRow.Hidden = False Then

            If filteredRange Is Nothing Then
                Set filteredRange = rowRange
            Else
                Set filteredRange = Union(filteredRange, rowRange)
            End If

        End If
    Next rowRange

    Set GetFilteredTableRange = filteredRange

End Function
Public Function GetFilteredTableRange(ByRef targetTable As ListObject, Optional ByVal includeHeaders As Boolean = False)
    '/ given a table, return a range object that contains only those rows which are visible
    '/ Do this by looping through tableRows, adding all visible rows to a unionRange


Newlines
are
cheap.

In Python, you always aim to keep your lines shorter than 80 characters long. I personally think it's a good practice to keep that size as a guideline in other languages as well. Your first line is 120, 1.5x my proposed maximum.

Added benefit of trying to stick with a maximum is it keeps you sharp. You're forced to think whether it's absolutely necessary for that line to be that long. Long lines are not fun to read, so try not to make them longer than necessary.

Public Function GetFilteredTableRange( _
    ByRef targetTable As ListObject, _
    Optional ByVal includeHeaders As Boolean = False _
)
    '/ Given a table, return a range object with only the visible rows.
    '/ Do this by looping through tableRows,
    '/ adding all visible rows to a unionRange.


That's how I'd do it, but I'm not up to par with VBA coding standards.