I agree with Laurel's post. I wanted to provide an example to make some of Laurel and Andrew T.'s points clearer and add a little bit of my own commentary.
In the comments, you also said, "There could be any number of ways for that to happen such as editing triggering an bottom-of-the-post asterisk with an explanatory."
Here is a made-up question:
What it means by would in following sentence:
Yes, I would be willing to do that.
i check dictionary but can't find appropriate definition. What it means by would?
For the sake of this example, I "corrected" everything. Then your proposed solution is something like:
What does it mean by "would" in the following sentence:
Yes, I would be willing to do that.
I checked the dictionary, but I couldn't find an appropriate definition. What does it mean by "would"?
*Errors were corrected in this post. Please click for an explanation.
[OR]
*Here were your mistakes: mistake 1, explanation 1; mistake 2, explanation 2; mistake 3, explanation 3; mistake 4, explanation 4...
Like the others said, all this additional boldface is confusing and distracting. Boldface is also used to change the stress of a word. If I were to see all this bold text and didn't know the reason, I would ask OP to review the usage of boldface.
Providing a list of corrections and explanations in the original post would not be relevant in understanding the question and answering it. In that sense, it's a distraction, and part of the philosophy on SE is that questions are supposed to be presented clearly, without distractions, for the benefit of all visitors. Yes, the corrections are useful for the asker, but it would not belong in the OP.
Changes you make are already preserved and highlighted in the revision history (see point 4). So making corrections in bold seems redundant.
Your idea of an "asterisk" is already available, somewhat.
When you edit a post, a link to the revision history is clearly displayed at the bottom. I made an edit to your post as an example. Right now, it says "edited [time] ago", but eventually it will say something like
edited Oct 21 '18 at 3:43
When you make the edits, you get a chance to explain yourself using the "Edit Summary". That summary and the highlighted corrections are visible in the revision history.
Edit Summary: Minor edits for answer example
↓

Well, the Edit Summary is usually used to summarize your changes, but I don't think anyone would object to a brief explanation of the corrections made, e.g. "The first word of a sentence/title should be capitalized".
I agree so far that with the features we currently have, leaving a comment with a reference to the revision history is a good option. The changes are clearly outlined there and if you want to write a brief explanation, you can do so in the "Edit Summary".
As a side note, I'll admit, I don't worry too much about telling the user that I corrected their grammar. I think it's because finding the link to the edits and seeing the corrections doesn't seem too difficult. Indeed, we occasionally get questions from learners that ask about other users' corrections to their posts. I always imagined this to be the "natural" way to learn about their mistakes and the corrections. If they're curious or don't understand, they'll just ask.