I attempted to enter the UK through London and was asked some personal questions that really triggered me and I just answered them very vaguely and evasively because they made me feel uncomfortable and felt intrusive. They cited concerns about my finances in the refusal letter even though the details they cited were simply incorrect.
I was detained for some hours, my biometric profile thoroughly taken, and then removed on the next flight back to the USA with the below stamp in my passport. I then researched my options and determined that my best bet would be to retry my luck with another entry attempt and if it failed then apply for a formal prior Visa. I thought it would be best to undertake all this from Ireland so I flew to Dublin and upon arrival I hand over my passport and the Irish border agent gave me a dirty look and asked me what went wrong in London. I explained and showed him the refusal of entry letter, and then he grilled me for two hours about my finances.
Finally he was barely satisfied (I love the Irish) and granted me entry to Ireland for 2 weeks (standard for US citizens is 90 days) and let me in.
I took a ferry to the UK and upon reaching the British port had my documents inspected by a UK border agent who neglected to stamp my passport but cordially granted me entry, what I assume was a standard leave to enter, equivalent to a 6 month standard visitor Visa, prohibiting me from working or recoursing to public funds.
My question is mainly which part of the pictured stamp indicated to the Irish fellow that I'd been refused entry, and should I expect that to cause me problems crossing other borders in the future?
Further, would changing my name and replacing my passport avert these problems?