《朗文》确实指出especially不能用在主语之前开始一个句子：

GRAMMAR: Word order

• Especially is not used at the start of a sentence before the subject.

• You say:

I like Thai food especially.

I especially like Thai food.

✗Don’t say: Especially I like Thai food.

• You say:

Young people especially are being affected by the economic crisis.

✗Don’t say: Especially young people are being affected.

但COCA语料库却有不少especially开头的句子，而且这种以especially开头的句子都采用部分倒装结构。

It cannot be too strongly asserted that in substance the text of the Bible is certain. Especially is this the case with the New Testament.

To anyone who truly loves America, nothing could be more inspiring than to contemplate this rededication of our youth, on each school morning, to our country's true meaning. # Especially is this meaningful as we regard today's world.

In these cities we are to have houses of worship, as memorials for God, but institutions for the publication of our literature, for the healing of the sick, and for the training of workers, are to be established outside the cities. Especially is it important that our youth be shielded from the temptations of city life.

A start, a fidgety shifting of the position, yes, even a violent sneeze, has been known before now to prove fatal to the incautious, and to nip in the bud many a promising friendship. Especially is this true among the lower classes of the Triangles.

A military judgment based upon... racial and sociological considerations is not entitled to the great weight ordinarily given the judgments based upon strictly military considerations. Especially is this so when every charge relative to race, religion, culture, geographical location, and legal and economic status has been substantially discredited by independent studies made by experts in these matters.

Whoever her date is, they'll be there smiling, good-looking and kind of heart. Especially will they smile at me, and take me in to live with them.

The committee report the bill back without amendment, although there are certain features thereof which might well be changed or modified in the hope that the bill may not fail of passage during the present session. Especially would the committee have otherwise recommended amendments, substituting for the expression,' labor and service,' whenever it occurs in the body of the bill, the words' manual labor' or' manual service,' as sufficiently broad to accomplish the purposes of the bill, and that such amendments would remove objections which a sharp and perhaps unfriendly criticism may urge to the proposed legislation.

You, all of you, who came along and suffered the throes of the WCG from about 1968 until -- well, whenever you managed to escape -- deserve my apology and I ask that you accept it. Especially do I ask the forgiveness of those who actually were children attending any of the meetings at feasts or in my own pastorates where I was the offending Lord of the Day, pounding the bible and my words into your brains.

This includes listening diseemingly enough both to his principal to fit into his intent and to the needy client to fit this latter's mentality. Especially does it include a twofold discovery or invention.

especially可以作为焦点副词，对句子中的某个词、词组或分句加以突出、强调。焦点副词通常位于其强调的词、词组或分句之前。例如以下句子：

I made it especially for you. 焦点副词强调for you.

A plentiful supply of water is especially important in summer. 强调形容词important。

The car is quite small, especially if you have children. 强调if从句。

Children are expected to obey their parents at all times. This is especially true of girls. 强调形容词短语true of girls.

最后这个句子如果especially移到is之前，This especially is true of girls. 则为强调整个谓语部分（即系表结构）。在这种情况下，如果需要进一步强调谓语部分，则可将especially前置于句首，同时句子采用部分倒装，提示especially作为焦点副词是强调谓语部分的。Especially is this true of girls. 这就是网友提问中的句子结构，也是语料库的例句的句子结构。

由此我们可以得出结论：Especially通常不能位于句首主语之前位置。但如果especially强调的是句子的谓语部分，则可以将especially前置于句首，同时句子必须采用部分倒装结构。朗文词典指出especially位于句首的句子错误，是因为没有倒装。如果朗文的句子倒装，应该就不是错句了。例如：

Especially I like Thai food. （错误）

Especially do I like Thai food. (正确）

最后回答你的问题：especially通常不用于句首。但在强调的情况下如果especially位于句子之首，则句子必须部分倒装。