This is a sign of distinction.
In the abstract (p. 1) N1570 :
Changes in the previous draft (N1539) are indicated by the βdifferenceβ symbols on the right margin: the deleted text is marked with the symbol '' *, new or changed text with ''.
In project N1539, alignof was a keyword appearing in the first row of this table:
The N1750 dropped alignof and replaced it with _Alignof .
Placing "*" looks a bit odd, but it definitely doesn't apply to the * operator.
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