"As part of" versus "as a part of"

Solution 1:

The difference between "as part of" and "as a part of" is essentially the difference between part and a part.

As part of this community, I feel the need to express my opinion.

Your comment is useless, as a part of my recent comments is.

In the first case, part is used with the meaning an element or constituent that belongs to something and is essential to its nature. In the second case, part is used to mean a piece or segment of something such as an object, activity, or period of time, which combined with other pieces makes up the whole.

Other phrases uses part, and would have a different meaning (or no meaning) if they would use a part.

We have come here to take part in a major game. (Take part means join in.)

Solution 2:

It depends on the speaker/writer. If the part can be separated from the whole, use "a part."