rainbow_csv has content-based csv/tsv autodetection mechanism enabled by default. This means that package will analyze plain text files even if they do not have ".csv" or ".tsv" extension. You can disable content-based autodetection mechanism at the package settings page.
Rainbow highlighting can also be manually enabled from Atom context menu: 1. Select a character that you want to use as a delimiter with mouse. Delimiter can be any ASCII symbol, e.g. semicolon 2. Right mouse click: context menu -> Rainbow CSV -> Set as separator ...
You can also disable rainbow highlighting and go back to the original file highlighting using the same context menu. This feature can be used to temporary rainbow-highlight even non-table files.
When manually enabling rainbow highlighting from the context menu, you have to choose between "Standard" and "Simple" dialect.
sell,"15,128",23%will be treated as 3 columns, because the second comma is quoted. This dialect is used by Excel.
Good catch. Let us know what about this package looks wrong to you, and we'll investigate right away.