Commenting
Commenting on the category
Commenting on a category can be done by clicking on the comment icon
The system will then display you a box where you could write your comment and send it
Reading comments and replying them
If there are existing comments on an entity, the comment icon at the top will be different 
Clicking on this icon will display the existing comments.
In addition to reading the existing comments and writing a comment yourself you may do the following:
REPLY : Reply to existing comments. Please note that you cannot reply to replies
LIKE : You may state that you've liked this comment
DISLIKE : You may state that you've disliked this comment
The number between the up and down arrows shows the sum of likes minus sum of dislikes.
SPAM : You may report that this particular comment is SPAM (i.e. not related to ICD, may be an advertisement, etc.)
Commenting on specific properties
If you'd like to comment on a specific parameter (i.e. title, definition, inclusion, etc.) than it is better to attach your comment to that parameter. This can be done by using the smaller comment icon near the parameter that you'd like to comment on.
The example below shows how to write a comment on the title of a category
Again if there are existing comments you may see them by clicking on the 
icon. From here you may reply to the existing comments or add your comments, etc.