Currently it doesn’t seem like img-tags get styled at all. At least in the default theme they don’t have properties set, even the most evident one which makes them responsive:
Specifically:
img {
max-width: 100%;
}
Without this rule, images just easily break your layout, whatever it is.
For example, here are two images being used in a table:
As you see the table got broken: it exceeded the size of the container and rendered the document unreadable.
We could have forced tables to use the fixed layout, but that brings lots of well-known side-effects, besides the mentioned fix also repairs the table:
So the question is: how comes that this obvious rules was missed in the default theme?
It was not easy to resist not to throw it in bugs, but still it’s a feature request.