Hey @Carson_Townsend this comes down to how dates are handled in Coda (and in ‘coding’) generally.
Each date and each time is actually a ‘date time’ - a value that contains both a date and a time. Coda will allow you to specify a column as a Date type, and it will only show the date, but this can be tricky because the time still is there, albeit hidden.
When using just dates, the time value defaults to 12:00:00 AM or in a sense ‘zero’, the lowest possible value for the time. Today() behaves in this way; when you use that formula it will return a date value with the time as 12:00:00 AM.
Modified() returns a date time as well - the date the row was modified as well as the time.
So when you compare a modified() value to a today() value, unless you modified the row at exactly today at 12:00:00 AM, the values will not match. Good luck!
Disregard my previous comment; both ToDate() and DateTimeTruncate("day") strip time properly.
Is your thisRow.[Date Completed] column an input or a formula? Because it looks like Modified() simply returns blanks for formula columns and would only work for input columns.