SWB, I did not object to the cap. I was disappointed, but had no choice in the matter than to accept.
Due to the unusual nature of them refusing or themselves being unable to remove the cap, I still have the chat protocol.
On 4/10/2017, I tried to buy some W7L@LSE. Most of the trading volume regarding those AIM stocks is done outside the exchange/ OTC; IB only offers the direct exchange access. There is no continuous trading, only a couple of auctions a day. To make matters worse, market maker bids and asks are indicative only i.e. they may not be honoured. The price was rising steadily at the time (due to continuous trades happening off exchange, but still being displayed in TWS "last" column). Bid was 180, Ask 185. I decided to place a buy order limit 188 to increase the likelihood to get an execution, but was capped at 185. Market maker did not honour the ask, there were no further orders for this auction, and thus no trade. I had to wait for the next auction one hour, and then 2 hours later during which the price continued to rise elsewhere.
On that day, I chatted with IB twice, once with a HK rep (that was early morning) and then Zug, Switzerland. They both independently of each other told me they could not remove the cap, but they understood my frustration and that IB management was discussing these caps.
