Featurewriter truncating a key column should issue a error.
When featurewriter is writing to ie Oracle, the columns are truncated to the length spesified of the featurewriter format, before the insert is done in the database.
If you update features, you specify a key column for the update. If the featurewriter is truncating the data to match the feature definition, then the data entering the database is not what you feed into the featurewriter. This is difficult to detect and cause ie deletes and updates not to happen because the key is altered, and no match in database is found.
So when data entering the featurewriter that exceed the length in the format definition, is a key, then a warning or error should be issued.
Or, if the column is a key, it should give an error, or if not a key, it should give you a warning.