SharePoint custom field definition considerations

When defining custom fields in XML for SharePoint, the element has numerous attributes and most of them are optional. It's important to think through.

I recently came across some fields defined with Sealed="TRUE". This attribute prevents the deletion of the column from a list once it's added (either added directly or by adding a content type that has this field). It's a good idea to enforce metadata consistency this way. However, what if a user mistakenly add a content type that has this field to a list, and then want to remove it? Well, there's no way unless writing a utility to delete it from the list using the API:

int fieldCount = l.Fields.Count;
for (int i = fieldCount - 1; i > -1; i--)
{
SPField f = l.Fields[i];
if (f.Group == "MyGroup") //or other criteria
{
Console.WriteLine(f.StaticName + " " + f.AllowDeletion.ToString());
f.AllowDeletion = true;
f.Sealed = true;
f.Delete();
}
}
l.Update();

There is also the attribute of AllowDeletion. Interestingly, If AllowDeletion="TRUE" and Sealed="TRUE", the column can be deleted. AllowDeletion appears to have precedence. Need to do some research to figure out the exact differences between the two.