Scrolling horizontally is hard. Warning someone that posts code that is larger than 80 characters against the readability problem this causes would be a solution to avoid then from the start.
The number of characters at which horizontal scroll bars are produced is not universal. See:
Since I asked that question I am using a different system, and now the max char width does not change with zoom, but it is still nonstandard (currently 87 characters).
Ow Ow Ow.
I have a cramp from scrolling horizontally....
Yes I am being facetious.
How is it so hard to scroll horizontally?
If the code is that long, that is what will happen, I see no reason to discourage it unless it makes it so that you cannot read the code.
But if you take that above sentence and put it like this:
YES it is very uneasy to read.
In that situation I would discourage the post, but how is the system to know the difference between that and: