You need to wait until the site refreshes your backpack. The site can't keep your backpack items updated in real time.

This is on the Todo list for the site.
https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/6/540742667857906012/

Usually people use the Offers placecard, and make it an unusual quality.
http://outpost.gg/no/m4jyac.png

Try resetting your browsers cache, also check that you dont have any plugins running that could be interfering with the site.

You can't call out users here, tell your friend to report them on the site/steamrep.
https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/0/558747922562007365/#c540742485382239358

To your first suggesion:
https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/6/666826166345755101/

Add option to disable the "Add on Steam" button.

To your second suggestion, there's always going to be people that don't read your notes, the easiest solution is to just remove/ignore the user and move on. Implementing an entire questionare system is unnecessary for the site.

Advertising is not allowed here.

Do not necrobump.

https://steamhost.cn/steamcommunity_com/groups/tf2outpost/discussions/0/558747922562007365/#c540742485382216907

Ban appeals aren't allowed here. Read the info in the link above.

This isn't the place to report/call out users. Do so through a report on the site.