Dukascopy did something similar for their Manual Trader's Contest.

Before hitting the market order button, you would have to include a comment of why you entered the trade.

Same for when you exit the trade.

also on your Own profile for the contest, you can see a Price Graph of where you entered and exited.

now it doesn't need to be the same , but how about this.

THe MYFXBOOK EA has an option ' record Comments'

The EA would have to
1.) create a text object on your Mt4 chart that is attached with the MFB EA
 a. The user than would add a comment within the text object ' Price at Yesterdays pivot'
2.) EA would Read the comment's within the Text object
3.) EA then sends the comment string

4.) when trade is closed - EA creates a corresponding Text Object
  a. The user than would add a comment within the text object ' Price bounce success - TP hit'
5.) EA would Read the comment's within the Text object
6.) EA then sends the comment string into the original's trades comment box, ensuring the first comment does not get overwritten.

The text objects can and would be placed on the chart in a numerical way for easy reference. A second object can be placed at entry and exit that corresponds to the trade # taken.

what do you think?