This issue arose in connection to the question Is this a $C^0$ foliation of $\mathbb{R}^2$? where a foliation is described formally. I thought it would help to have a picture of it. Initially I wanted to place it in a comment but discovered that I cannot do it - only a link to the picture appeared in the comment. So then I placed it in form of an answer, with a warning that this is just an illustration rather than an answer.
Earlier a similar situation occurred with an answer (to the question Pathological product space norm) rather than the question itself.
So my question is what would be an appropriate way to illustrate others' posts? I could in principle edit the post itself, I have enough reputation points for that, but (a) is this ethical? and (b) what about those who don't have enough points?
Creating a separate answer bothers me simply because it is not really an answer, so in particular earning points for it (which is quite easy) is sort of not fair...
Could some new form of post be created for illustrating others' posts, or maybe just allow images in comments? Or maybe it is possible and I am simply doing it incorrectly?
PS
Although I've accepted an answer which I think provides the optimal thing to do in given circumstances, the discussion that followed made me realize that probably I should formulate what I want more clearly.
The main point probably is that such illustrations have a status different from that of genuine answers. They might be useful and may deserve reputation points as such, but not in the same way as genuine answers. I have no idea how exactly to differentiate but that's why I am asking a question :)