You're not technically supposed to "choose a style" in that dialog. The style selector should be prepopulated with the correct style choice for your current map.

If you want to use drawing tools belonging to a different map type than the one you are working in, you need to import the appropriate fill styles first. More about this in this faq topic:

You can't. There is no way for one member to block others seeing what they post. Besides, this being a public forum, people can browse it and look at the images even without an account at all, so banning wouldn't really work even if you could.

For comments, if someone is sending abusive comments or engaging in undesired behavior, you should report them to a moderator. If it was done via private messages, you can add a moderator to that conversation so they can more easily see it themselves.

1. That's highly variable. The length of the platform is typically related to the length of the longest train stopping there, which is again dependent on the number of passengers in peak periods. But I've also traveled to subway stations that are actually to small to accommodate the entire train, so they usually announce on the PA system that if you want to get off, the X rear doors won't open, so start moving. But going with a length approximately similar to the train length itself is a good starting point, at least based on my own experiences.
2. I'm not an expert on that and don't fancy running the calculations myself, but this wikipedia page has some interesting data and formula: https://en.wikipedia.org/wiki/Minimum_railway_curve_radius
3. There is both a dimpled texture (but perhaps not close enough, and it is black) and some nice black&yellow hazard stripes in the @Bitmaps\Tiles\Storyweaver HighSpace folder

You'll have to :CC2EXPLODE: the symbol, that gives you access to the individual parts of it.

I have a blog article about X'es that might help you: