If my badge from shields.io:
β β β β it displayed as block element on GitHub.
elif my badge from another service:
β β β β it displayed as inline element on GitHub.
I don't think, that badges displaying as block element β it expected behavior.
See https://github.com/Kristinita/SashaShieldsIoDebugging repository:

python, wheel and commitizen badges β from img.shields.io.
See source of my Readme.rst .
In PyPI site all my badges β from shiels.io and another services β display as inline elements:

Thanks.
This appears to be a quirk of the way GitHub renders RST. I can't reproduce it in another RST Editor. As a workaround, if you set a link target on the badges, that will get them to render inline. I've forked your repo to demonstrate. See:
https://github.com/chris48s/SashaShieldsIoDebugging/blob/master/Readme.rst
https://github.com/chris48s/SashaShieldsIoDebugging/commit/27cd54957bdf219e0e5e4874eef46b41bb58de0e
I expect if you remove the link targets from the other badges you'll probably see the same behaviour but I have not tested it.
Thanks! @chris48s, maybe you add in README, that target necessary for GitHub?
Most helpful comment
This appears to be a quirk of the way GitHub renders RST. I can't reproduce it in another RST Editor. As a workaround, if you set a link target on the badges, that will get them to render inline. I've forked your repo to demonstrate. See:
https://github.com/chris48s/SashaShieldsIoDebugging/blob/master/Readme.rst
https://github.com/chris48s/SashaShieldsIoDebugging/commit/27cd54957bdf219e0e5e4874eef46b41bb58de0e
I expect if you remove the link targets from the other badges you'll probably see the same behaviour but I have not tested it.