I've used other platforms where a general chat thread with the athlete exists, and it's a much more natural way to check in and find out how things are going, discuss how they are managing lifestyle factors such as sleep, hydration and nutrition which don't pertain to a given training session and talk about big picture goals. Clients don't want to download multiple apps and services and from a coach perspective, it's much more professional and makes it easier to manage work/life balance compared to connecting via WhatsApp, which I have tried in the past.

Edited to add: Notes could fulfill this function, but they need to have a notification function (optional would be good) and to be searchable in the calendar search tool.

An in app messenger is a critical part of coach athlete communication. Keeping the messaging back and forth in the same app that athletes use to see the workouts, and provide subjective feedback is way better than doing that all via email, text, comments/ notes or other outside methods. This is a MUST to be competitive with other coach personal trainer apps that are out there.

Chat box between coach and athlete integrated would be interesting.

So the comments after a workout are good, but would be great to include a communication channel between coach & Athlete, like WhatsApp.

Not sure if this exists and I'm unaware of it, but I'd love a running chat window to communicate with my athlete beyond individual notes on individual workouts.

I text or email with some of my clients on non-workout specific issues and I'd love to be able to do this within the platform. A basic version would be just an ongoing conversation. A more mature version could be topic based, so a convo could be grouped by topic

Is there a way to communicate with the coach? For example, can I ask him general questions within the Training Peaks App (not externally via email, of course I can always do that)? The answer is no.

And secondly, can I ask him specific questions about a workout in the future? The only option I see is to leave a post workout comment, but what if I have a question about a specific workout in the future, do I need to ask this question via the 'post workout comment' field (and will he get notified if I ask a question?) or is there another way (other then emailing him which of course I can always do) The answer is no too.

This was all possible in TodaysPlan (via an extra notification center), but I cannot find it in Training Peaks. It would be great if Training Peaks can create such a feature.

I recommend putting in a stand alone inbox for the management of athlete communication. If the inbox has adjustable setting on what notifications you would like to see this would be even better so you could turn off all the workout upload notifications and metric notifications.
The current setup of notifications that training peaks has it is easy to lose messages whereas a standalone inbox allows you to see all athlete communication a lot easier.
A search function would further improve functionality allowing you to search for certain athletes or time periods, read or unread messages will improve functionality.
In addition an easy way to swap between read and unread for the messages this would be great rather than just once it's clicked on it is read and it stays that way. It will allow coaches to stay ontop of messages they have actioned and those they haven't.
Today's plan had all of this functionality and it helped amazingly with coaching work flow and allowing easy and effective communication.
If done well it could be combined with more precise notifications like only notifying abitj workouts when it doesn't match scheduled workouts or metrics in certain ranges etc.
Similar to this https://www.todaysplan.com.au/2019/06/all-your-communication-solutions-on-one-platform/

An integrated Chat between coach and athlete.
A personal chat (like Telegram, WhatsApp...) with every athlete, where the Coach can answer alto to the comments for every single training.
I think that so you can have a better and faster communications with your athletes about their training.

Maybe with the option enable/disable chat with a particular athlet

I love this idea and should be an important function in the future.When this gets into the development

As someone who works with a lot of junior athletes and has to worry about communication from a safesport perspective, it would be awesome to see an in-app messenger. This would allow all communication to take place in one central location and allow parents to monitor all communication.

Trainingpeaks makes a difference today. But we must make sure that it will make a difference in the next decade. With the arrival of AI and machine learning, one way to make a difference is coaching and customer relations. I think it is critical to add a Wall or chat service per athlete. And integrate everything under the universe of trainingpeaks.