Your email reader is supposed to help you read and reply to message threads.
> not being able to browse code
You browse code by doing a git clone/checkout, and then using your regular programming tools.
> no convenient links
Your email client should help you navigate and search message threads. Here is one of many that helps you do this: http://www.djcbsoftware.nl/code/mu/mu4e.html
> no formatting
This is what you editor is supposed to do.
> no branch visualizations
This is what tools like magit are supposed to do: https://magit.vc/
> release notes being easily accessible
They go in a text file in the repository. You open the text file with your editor. Your editor should also help you write release notes: https://www.gnu.org/software/emacs/manual/html_node/emacs/Ch...
> having to set up a bunch of fragile text based filters.
Why?
I see arguments like yours about email and git a lot. Why do you think people disagree with you? You have to pay attention to what you are really saying. You are not listing advantages of web-based git interfaces. You are listing "disadvantages" of existing tools. And all of the "disadvantages" you list are really areas where you do not understand how to use Unix programming tools effectively. Getting off of webmail and onto a good text-based email client is one of the best things you can do as a computer user.
I am not stating an opinion. I am making a judgement. I can do that because I have the requisite knowledge and experience. You do not - as you yourself stated, you "don't want to spend time configuring or fixing [your] email solution." (another tell-tale sign is referring to "the terminal.") Stop trying to make virtue out of your choice to be ignorant. Stating that most people will prefer GUIs is not an argument for anything ("X is popular" is never a good argument for anything) - most people have not had any exposure to alternatives like text-based tools and therefore cannot have any meaningful or informed opinion on the matter, which you pretend to do. Your choice to be ignorant of something does not entitle you to make judgement calls about the things you are ignorant about. You can say "X is difficult to learn/do" (true), but when you argue that "X is an inferior tool" with someone that has some expertise in the subject and in X, you just come across as a fool.
I can see how it would be inconvenient for people who use an inflexible email client or editor, though. (I'm trying to make this workflow a little less intimidating for Guix by working on a more convenient web interface on top of debbugs.)