user22057: Yesterday an answer I posted to a question was flagged with the following notice:

Want to improve this post? Add citations from reputable sources by
  editing the post. Posts with unsourced content may be edited or
  deleted.

I have no objection to this in principle, although was a little surprised that the moderators had not left a comment to which I could reply when I had fixed it. After the original poster had confirmed my interpretation of the question (the ambiguity being one reason for the brevity of my answer) I conducted some time-consuming research and then revised the post, providing extensive references, explanation and illustration. 
Twenty four hours have elapsed, and the flag still remains, suggesting to readers that my revised answer still contains unsourced content. Hard cases make bad law, and I am not in the habit of complaining about an individual case. My point is that in these circumstances one has no way of communicating to the moderators that the answer has been fixed. 
I think that that needs fixing.

user5144: Unfortunately there is no way to to see any changes automatically when this flag has been used. It is used regulary, so it simply happens that the removal is forgotten. I also don't have a look at every post, especially when they are written by experienced users. So, as @AliceD wrote: Simply flag the answer with a comment that this is resolved.

user16866: I agree with the other answers, but let me expand a bit for future users: 
Simply flag the post (selecting "in need of moderator intervention") and request that a moderator look at it to consider removing the notice. 
If a moderator has commented directly on the post that has been assigned a notice, then simply pinging that mod in a comment below the post using the "@" symbol and mod's name with a request to remove the notice will work, too.
Of course, a mod may decide that ample improvement has not been made, and they may leave the post notice intact. Most times in that case, the mod would leave a comment either below the post or along with the declined tag addressing further concerns or suggestions. 

In your case, ample addition to the post was made and so the notice was simply removed. Typically, if major improvement has been made or if a new user has taken initiative to improve a post to put it in line with our site's expectations, I like to leave an encouraging comment as positive reinforcement. (I typically delete the comment later as "no longer needed" unless it can stand as a teaching moment for others -- this depends on context). 


user9943: Nice update on the post! The banner is removed. Next time, you can simply flag your question for mod attention.

22057: <p>Yesterday an <a href="https://biology.stackexchange.com/questions/92230/can-an-infectious-diseases-come-from-a-plant/92243#92243">answer</a> I posted to a question was flagged with the following notice:</p>

<blockquote>
  <p>Want to improve this post? Add citations from reputable sources by
  editing the post. Posts with unsourced content may be edited or
  deleted.</p>
</blockquote>

<p>I have no objection to this in principle, although was a little surprised that the moderators had not left a comment to which I could reply when I had fixed it. After the original poster had confirmed my interpretation of the question (the ambiguity being one reason for the brevity of my answer) I conducted some time-consuming research and then revised the post, providing extensive references, explanation and illustration. </p>

<p>Twenty four hours have elapsed, and the flag still remains, suggesting to readers that my revised answer still contains unsourced content. Hard cases make bad law, and I am not in the habit of complaining about an individual case. My point is that in these circumstances one has no way of communicating to the moderators that the answer has been fixed. </p>

<p>I think that <em>that</em> needs fixing.</p>
 5144: <p>Unfortunately there is no way to to see any changes automatically when this flag has been used. It is used regulary, so it simply happens that the removal is forgotten. I also don't have a look at every post, especially when they are written by experienced users. So, as @AliceD wrote: Simply flag the answer with a comment that this is resolved.</p>
 16866: <p>I agree with the other answers, but let me expand a bit for future users: </p>

<p>Simply <a href="https://biology.stackexchange.com/help/privileges/flag-posts">flag</a> the post (selecting "in need of moderator intervention") and request that a moderator look at it to consider removing the <a href="https://meta.stackexchange.com/q/339700/309922">notice</a>. </p>

<p>If a moderator has commented directly on the post that has been assigned a notice, then simply <a href="https://meta.stackexchange.com/q/43019/309922">pinging</a> that mod in a comment below the post using the "@" symbol and mod's name with a request to remove the notice will work, too.</p>

<p>Of course, a mod may decide that ample improvement has not been made, and they may leave the post notice intact. Most times in that case, the mod would leave a comment either below the post or along with the declined tag addressing further concerns or suggestions. </p>

<ul>
<li>In your case, ample addition to the post was made and so the notice was simply removed. Typically, if <em>major</em> improvement has been made or if a <em>new</em> user has taken initiative to improve a post to put it in line with our site's expectations, I like to leave an encouraging comment as positive reinforcement. (I typically delete the comment later as "no longer needed" unless it can stand as a teaching moment for others -- this depends on context). </li>
</ul>
 9943: <p>Nice update on the post! The banner is removed. Next time, you can simply flag your question for mod attention.</p>
