A bug in displaying the site when clicking on a link with an anchor. why is that?

Question

css

Hello.
there is a
demo.braiteck.ru/page.html layout (normally displayed),
but if you follow the link demo.braiteck.ru/page.html#comment-3
, the top part of the site content flies somewhere.
the culprit is identified - this is aside:after
it seems to lack space and it shifts everything, although it has position: absolute; and shouldn't have any effect.
the bug is observed in chrome and mozilla and probably in other browsers.
the solution, of course, was found in the layout how to get rid of the crookedness. but purely sports interest is of interest, how can this be and what is the reason for such behavior? maybe someone knows or can figure it out and explain.

Answer 1

Here's the culprit:
.main_bg {
background: #fff;
box-shadow: inset 0 0 32px rgba(124,124,124,.3);
border: 1px solid #fff;
/* overflow: hidden; */
}