(Part 1) This is a tough one. It touches on cultural details and writing style. In ordinary writing, virtually all authorities on style recommend using the active voice. It is stronger and clearer. It is usually "good style." The passive voice allows writers to avoid using a subject. It is often used by administrators who want to evade responsibility. It is much more comfortable to say "Mistakes were made" than "I made mistakes." The passive voice can be used half-intentionally _because_ it is boring. Someone may not want people listening too carefully to what they are saying. They may hope few will notice some unpleasant detail, but that later on they can say "Oh, I didn't hide anything, I was clearly on record as saying it." The passive voice is also a way of taking ego out of the picture. This is one reason why it is often used in scientific writing. If someone writes "A Wilcoxon signed-rank test was performed," that communicates the important information. If someone writes "I performed a Wilcoxon signed-rank test," it makes a reader want to say "Who cares? Do you think performing a Wilcoxon test makes you a big deal?" The passive voice sounds authoritative, dignified, and pompous. Starting sometime in the mid-1800s, scientific papers started to emphasize the passive voice, and this is now a tradition. Even in science, one reason for using passive voice can be used as a euphemism. For example, instead of saying "I killed the lab rats and examined them," a paper will say "The animals were sacrificed and a post-mortem was performed." So, your problem is that using the active voice will probably improve your writing, in terms of style. At the same time, you are taking a risk because your writing style may be different from what is usually seen in some kinds of academic writing.

(Part 2) I definitely would NOT simply accept all of Grammarly's corrections. I don't know Grammarly, but I can tell you that other grammar checkers, such as the one built into Word, are unreliable. My best advice, seriously, is to look at some recent papers, in English, in your own field, that have the same audience as yours. For example, if you have the ambition of publishing your paper, think about what journal or magazine you'd like to submit it do, and read some recent articles in that journal. See how other people in the field are handling issues of style: personal versus impersonal, active versus passive voice, and so on. For example--knowing nothing about this--I browsed a journal access site and chose, at random, "Frank Furness and Henry Holiday: A Study of Patronage, Architecture and Art," George B. Bryant, Architectural History, Vol. 56 (2013), pp. 169-21. A sample is included below. The article is written mostly in the active voice. The writing style is that of good, "educated" expository writing, similar to magazines like "The Economist" or "The New Yorker." The only thing that makes it a journal article is that it is very careful and precise, and treats of a very narrow subject area. But the style is clear and strong. The point I want to make is that whenever the passive voice is used, there is an obvious _reason_ for it. See the next part for examples.

(Part 3) "Soon after this window was installed, one of the Bradford daughters wrote to the Board of Trustees complaining about the excess light falling on it through the clear glass window in the south wall of the transept, and requesting that the transept be covered by some sort of shade. More than a year later, the Trustees agreed to place a grey shade over the window at their expense, but this did not function well, and, in April 1891, the Trustees asked the Property Committee to find another solution. The shade was removed but the problem remains unsolved to this day, involving the balancing of light level." He writes "the window was installed" because he doesn't know who installed it. He knows who complained (Bradford's daughter) and who responded (the trustees), so these are in the active voice. "The shade was removed" uses the passive voice because he isn't sure about the details. "The problem remains unsolved" is also intentionally vague. He knows the problem hasn't been solved. He has details about the first attempt, but he doesn't have details about whether anything else was ever tried, or who tried it. He just knows that it's 2006 and there are still problems. Every time the passive voice is used, it is used for a reason. It's my opinion that every time you use the passive voice, you should ask "do I have a good reason?" If the active voice can be used without changing the meaning, consider changing it. But the passive voice can be used just for variety. It might be used to emphasize parts of the sentence through word order. For example, "John Jakob Raskob built the Empire State Building in 1931" leaves us with "1931" as the last word. "In 1931, John Jakob Raskob built the Empire State Building" leaves us with "Empire State Building" But if we want to end the sentence with Raskob's name--perhaps because of what comes next--we could write "In 1931, the Empire State Building was built by John Jakob Raskob."

Excellent explanation by Dan Smith! I'm going to bookmark it.

Thanks a lot, Greg for your explanation and kind advice. I really appreciate it.