Through the cog in the top right corner of the post. Note that you can only delete a comment, not a topic. The latter is due to how the developers wrote the forum software, since deleting a topic would also mean deleting all the comments of the topics (which probably don't belong to the poster of the topic), so they simply did not allow users to delete topics (even if there are no comments yet)

Actually @jslayton, it is the opposite way around. If you don't hold down shift, all effects are wiped and the new preset is applied, but if you hold down shift, the current effects are kept.

It is certainly not normal behavior for CC3+ to intermittently show red X'es for images that worked earlier, but there are a few external factors I can think of:

• If you have the CC3+ data directory on an external drive like Thescabi mentions, it may be an issue with the drive or connection to the drive. Could also happen with an internal drive if the drive itself was bad.
• Your antivirus is a bit too greedy. Antivirus software often scan files that are opened, and while it does that, it denies other software access. If it keeps the file locked for too long, CC3+'s request may time out, which means it fails to load the file. If this is the case, just hitting :CC2RESMODE: and clear the bitmap cache, check "redraw on ok" and then hit OK should force CC3+ to reload all bitmaps.
• Either the actual bitmap on disk the drawing refers to have been moved, OR if the image is set up with a map-relative path, and you moved the map file but not the corresponding files (The latter is really only a possibility witch custom artwork though, not with the standard symbols and fills from CC3+ and add-ons). You already mentioned you didn't move things, just kept this point here to have a complete list.

Trace have an unfortunate aversion to smooth polys. You can usually get it to work as desired by turning them straight temporarily, trace, and then turn them smooth again.

As for going the wrong way around, it will do that until you have moved your mouse far enough from the starting point that you pass the selection point. Trace always go through the selection point, so if you haven't moved your mouse far enough yet to pass the selection point, it is forced to go the other way around to be able to go through it. I usually always make my selection point quite close to the starting point (but far enough away that I am 100% sure it is on the right side of it) to minimize this behavior.

It is a bit difficult to see the end result. Could you make it a bit more visible to be closer to the visibility of the paving on the pier?