Or just type the coordinates on the command line. Place the first corner normally with the mouse, then enter @70,15 on the command line for the second corner.

See this FAQ entry:

My drawing tools are missing their textures (or show incorrect textures)

Unfortunately, it is very difficult to stop single spammers posting a single post. As long as a physical human being is willing to spend the time and register manually on the forum, it is impossible to stop them without also be very hostile to legitimate newbies.

The forum is utilizing public spam lists to avoid those people jumping from forum to forum to register and spam, and it also have rate limits to prevent a spammer from doing things like filling the front page with spam (using manual or automated means), as well as edit limits to prevent the classic "post a generic but not spam post, and then go back and edit it after moderators have read the original post and moved on" but the single individual posts will continue to appear, and we remove them as soon as we notice. As already mention, use the Flag link in the post to report it.

Trace can be a bit weird when trying to trace a smooth poly because the nodes aren't located along the visual edge.

Try using Smooth to Straight (right click :CC2EXPLODE: ) on the poly first, then trace it, and turn it back into smooth using Straight to Smooth.

Use :CC2BREAK: to remove the parts of them you don't need. Remember you can use the :CC2MODINT: modifier to get the exact points where they cross.

Breaking a polygon WILL turn it into a line, but just continue working with the line until it is correct, and then you can turn it pack into a poly when done by right clicking :CC2EXPLODE: and picking Path to Poly. If you removed a corner during the process (which you will likely do, you'll need to add in a new one using :CC2INSNODE: to avoid a missing portion of the poly in the corner.

To make the two polys line up exactly against the border of one of them, start by trimming the light poly to the points where it meets the dark one, then make a copy of the dark one, trim it down to just that path segment where they share a border, and use Combine Paths to merge that with the light one, this will result in them both having a border in that space.

Note that it might also be simpler to delete the lighter poly, and assuming it is drawn using a drawing tool, simply use the trace feature of the drawing tool to follow along the edge of the darker poly.

Edit: Beaten by a little mouse, but with a very different approach.