For CSV AAVSO download format files, if the comment field (or any other text field) contains commas, this will cause VStar (or any other program) to misinterpret subsequent fields. In VStar this sometimes manifests as invalid observations with more than the max number of expected fields.
One way to handle this is to wrap each field in quotes. This is an option provided by spreadsheet apps like Excel.
Assigning to you Sara to raise with Doc et al since obviously this affects other consumers of AAVSO download CSV files.
For much more detail, see:
Although this is an annoying problem, it can be worked around by requesting TSV instead of CSV (assuming there are no tabs in comment fields etc, otherwise you have the same problem, different delimiter).