I've only just noticed this. I am not sure if it used to happen before, and I have only just noticed it, or it is something that is new.
Looking at the screen shot below:
The text under the first code snippet (which had no horizontal scroll bar) is nicely spaced, with a blank line between the snippet and the next paragraph.
The text under the second code snippet (which has a horizontal scroll bar), is much more tightly "bunched up" to the bottom of the snippet. There is no (or not much of a ) blank line between the second snippet and the start of the following paragraph.
It appears that the additional horizontal scroll bar is taking the space provided by the blank line.
It would be nice if the snippet with the scroll bar, provided an additional blank line, somehow.
As an update, it is particularly bad if a horizontal bar follows a code snippet, the scroll bar and horizontal bar almost merge:
Happens on Chrome Version 49.0.2623.112 (64-bit), and Safari 6.2.8, on OS X 10.8.5
Firefox 48.0.2 and Opera 37.0 are OK though.
Hmm... could be caused by out of date browsers...