Like tasks, Planfix comments can be added in different ways.
The quick option
In the desired task, click in the Add comment block:
A form for adding a comment will open, where you can enter text, links, quotes, and more.
The Plus sign icon next to the Planner section in the main Planfix menu. This opens a form for adding a new comment. You'll need to select a task where the comment will be added. One advantage of this method is that it's available from any Planfix section:
The classic option
Go to the desired task and click the "Add comment" button on the top panel:
You can create a new comment in the Planner section in the same way. Hover your cursor over the desired task, and a list of operations will appear. Click the "New comment" button:
A lesser-known option
Some actions are added by the system automatically, as a result of specific user activity. For example, let's say you moved a task in a calendar. Planfix would then add an action to the task about the modified completion date. Let's say you set a meeting in your Planner.
Planfix would then create a task and add a comment to it with a "Planned working time" data tag. Thanks to these automatically added comments, you can always see who did what in a task, and when: