Currently when one clicks "Help" in the lower right corner:

It opens a new window with instructions in it.
There are two refinements that would help here:
when this opens a new window, it should have "Help" in the name of the page instead of "Mattermost." This is confusing to users since they don't know what this tab is generally and some people tend to keep it open to see the help info. This should be "Help - Mattermost" or just "Help."
This help function should instead provide a small set of instructions at the bottom (below) the text input field with core options handy for review. For example:

Notice how the example text could shrink and expand based on window width. Further, the last link "Help" could actually change to "Advanced Help" and then that would open a page and a small x could go to the side of the help text.
Another option would be to follow the model of StackOverflow.com:

Hi @ylluminate, thank you for reporting this 馃憤
Let us know if you're interested in submitting a PR for these changes?
I also opened a ticket here for tracking: https://mattermost.atlassian.net/browse/MM-12793.
Thanks @amyblais! I truly wish I had the time to do PRs right now, but I'm just overwhelmed presently and it's not looking good for at least several more months. I'm trying to capture things I'm seeing with our users and I experience myself that would refine the UX as we go since we're relatively new with Mattermost from our migration from HipChat.
Oh, FYI, I think @ylluminarious committed a bevy of updates to the HipChat importer that should be helpful - I'm not sure if he's had a chance to reach out to you yet or not.
No worries!
I haven't heard from ylluminarious yet, but looking forward to hearing what updates have been made!
I'm not sure if this should be added to its own issue but I've also noticed that any additional window that is opened from the original help window will be automatically closed if you close the original window.
For example:
Thank you for the report @shiitake, I was able to reproduce this so I opened a ticket here: https://mattermost.atlassian.net/browse/MM-14010.
You are awesome @amyblais - I was not totally sure where to add it so I really appreciate your help.
Letting you know that the Jira ticket was closed with a note that it is already done as we provide markdown tips when typing. Changing the window name doesn't seem to be high enough value for the effort and continued testing mana. @ylluminate
That's sad to hear. The current formatting and help really sucks. The more and more I use Mattermost, the less and less I like the ability to control formatting. Having markdown is simply not enough and many of our users can't figure it out or can't hit things right. We really need to implement this if Mattermost is to remain viable - else perhaps formatting should just be yanked out altogether.