Linux has many desktop environments each of them has different kind of windows managers that provides window borders and window header with close,minimize buttons, etc.

Teams ignore window manager at all ant provides its own window controls for main application window.

This is looks ugly because it does no comply with system look and feel. Also there is no window borders so it is hard to resize main window.
No shadows and other effects, because most of them related to default windows manager.
Look into attachment how teams window looks that in placed over web page.

VS Code for Linux allows to use native window borders, Teams should add such option to.

Too much real estate
chat-content-to-app-window-size ratio is waaay too low. Only about 1/3 of my app's window contains chat content. A good chat app should display a rich chat history and occupy the bulk of the window space. Slack and Hipchat both did this much better.

What's wrong with single-flow chat?
The nested conversations make for an awkward message flow. This can make it difficult to find old messages in the chat history or to see recently posted messages

Now you see me ...
conversations auto-collapse after a certain number of messages (even for messages I haven't yet read!) and I routinely miss comments

What's with the "New Messages" toast notification?
Why doesn't it just show me the message (auto-scroll to bottom)

Moving target?
1. I'm not sure why/how but sometimes the scroll bar moves on me in the web UI and I end up chasing it with my mouse. Some sort sick, twisted game?
2. There are times I click in a reply box or start new convo box and start typing... but nothing goes to the screen, like I clicked out side the window in hipchat you could click anywhere in the page and start typing you didn't need to be careful where you clicked
3. Don't scroll too fast or you'll end up stuck on a welcome screen and can't get outta that until you quit the app and open it again (observed on macOS High Sierra)

Where is everybody?
For new users, it isn’t clear how to find other teams.

Team search is not functional
I've actually become less in touch with other teams because of this

Platform/OS support
1. Limited browser support, at least under Linux. As my primary browser is Chromium under Ubuntu, I have to either play a tedious masquerade game or launch Firefox just to use MS Teams.
2. No support for iOS9. Yes, iOS11 is the new-hotness (as of a month ago) but I am still on an iPhone that cannot upgrade to even IOS10. This was not a problem for me with HipChat, nor is it with Okta. Not even gonna try the Web version on mobile Safari.

Missing/Broken stuff
1. I can't upload an image or link that will display automatically
2. Every time I have attempted to drag and drop a file it fails. It is possible it a file size limitation, just tested hipchat with the same file I just used to test here and it had no problem
3. e-mail notifications seem to arrive late
4. No emoji/emoticons (seriously?)
5. MSTeams will not let me select multiple posts and copy them all together

On-line status
Trivial, but with hipchat it was really easy to see if someone was online so you knew if you messaged them they'd see it here it will show me the status icon, butI have found it to lie to me on several occasions

MSTeams insists on being overly formal
We liked the nicknames we could use in hipchat – it made conversations for personal.

Mysterions
What does the setting "Banner" mean under Settings -> Notifications?

So, I followed the advice given here: https://techcommunity.microsoft.com/t5/Microsoft-Teams/Where-is-the-best-place-to-report-bugs/td-p/32183

I posted a bug report here: https://techcommunity.microsoft.com/t5/Microsoft-Teams/Bug-report-Link-missing-when-hiding-large-text-body-in-Teams/m-p/169272#M12158

Apparently, it has been marked as spam, so Ill try posting the same report here:

I have been looking for the documentation for Teams Webhook Connectors. I did a Bing-search for 'MS teams webhook connector documentation' and found soemthing [1]. The documentation doesn't fully explain the purpose of all fields that can be included in the POST request. I hope there's a better resource out there, somewhere, but I highly doubt it.

To the point: An example webhook POST [2] specifies that the body of your message goes in the text-field.

While this is great, too much data in the text-field results in this message appearing the Teams-chat:
> This message is too long to display here. Please visit the link to read the content.

This is fine, if the link was actually included in the message, but alas, it is not. It should be there, but it isn't. This is now a bug report.

If you have any questions about how to reproduce, please just ask away.

Disclaimer; I am a long time Linux user, and I haven't used Microsoft products for many many years. Usage of MS Teams is being forced upon me, so please please please give me a great experience. I would love to have something good to remember from my newest experience with Microsoft.

Regards, Asbjørn

[1] https://docs.microsoft.com/en-us/microsoftteams/platform/concepts/connectors

[2] https://docs.microsoft.com/en-us/microsoftteams/platform/concepts/connectors#post-a-message-to-the-webhook-using-curl