不能说是“画蛇添足”。虽然这个 And 可以不用，但用了也不是错误。
and（因此，而且）, but （但是）和 for（因为），这几个并列连词，不仅可以引导并列分句，还可以引出独立的句子。虽然前面的句子用了句号，但与前文仍然存在这几种意义关系。

赞同刘老师的解答，当and, but, for位于句首或段首时，在意义上均与前句或前段有关联。以下例句都摘自是84版高中英语课本。

一、and位于句首：

1. "Sure," the doctor's voice says. "Well, he doesn't have a fever. And his pulse is fine. Now, breathe deeply, Charlie."

2.Once Aristotle made up his mind that heavy objects always fell faster than light objects, he taught it as a truth to his students. And because he was Aristotle, the great thinker, no one questioned his idea for almost 2000 years.

3.When I put them on, I shall be able to find out which men in my empire are unfit for their offices. And I shall be able to tell who are wise and who are foolish.

4.This they kept for themselves. And then they went on with their work at the empty looms until late into the night.

5.All the people in the city were now talking about this wonderful cloth which the Emperor had ordered to be woven for so much money. And they were eager to know how wise or foolish their friends and neighbors might be.

二、but位于句首。

1.I don't see anything. This is horrible! But I mustn't let anyone know.

2.He felt very silly, for he knew that the people were right. But he thought, "The procession has started, and it must go on!"

3.The next day Aqiao decided to go back to the valley with her brother. But when she opened the door, she found things had changed.

4.Every day, people throw away a lot of rubbish. Some of the rubbish, such as food, paper and iron, rots away over a long period of time. But plastics and rubber never rot. If they are burned, they give off poisonous gases.

三、for位于句首和段首。

1.Of course they could not look at him with their eyes, but they thought they might learn what kind of animal he was by touching and feeling him. For, you see, they trust their own sense of touch very much.

2. Della's fingers tore at the string and paper. Then an excited scream of joy, and then, alas! a quick change to tears.

For there lay The Combs - the set of combs that Della had worshipped for many months in a shop window.