The most common approach is to enclose such fields with quotes. There are many resources on the web that describe this. The flat file adapter in wM IS supports this.
Yes it can be done using quotes. But if possible, i would rather request the source which generates the flatfile to use “|” instead of comma delimiter. Because if you have user defined fields like names, street… etc. The probability of getting commas will be more random and whole parsing will go for a toss.
Its not a valid flat file if the comma (as data) doesn’t come with a release character. For that matter, any parser wouldn’t know what is separator and what is data unless you specify/instruct it. Refer flat file schema developers guide to know more about release characters.