Hi Stephanie,
Also coming from the UK, I have seen this a few times.
I honestly think that some folk simply have no idea about how they are acting, and they believe that just clothes and make-up are enough to pass in public. If people practice dressing alone they may never realise they have a "problem" until they get into a difficult situation. I really don't think you will see many "sissies" in the middle of the day on a train, dressed in jeans.
The most memorable incident for me, was when one such person appeared in a quiet bookshop while I was presenting male. They were in their 50's, had done an acceptable job on their appearance, and had a lot of confidence. Naturally I spotted them in a flash, but they would have got away with just an occasional glace from the other cisgendered people in the shop, if they had simply bought the item they picked, said thank you, and left....
...but no, with a really creepy slowly deepening voice, this person decided to comment on the weather, then they said they liked the shop assistants top, asked where she bought it, was she going out this weekend, did she have a boyfriend, did she like her dress..etc..etc..
10 seconds into the conversation any doubts about birth sex of this person had disappeared, but assistant kept a brave face and answered the increasingly personal questions as politely as she could. After 6 minutes this person left, and the shop assistant broke down in a pool of tears leaving the people in the shop, and her manager (who had been about to intervene) in no doubt about what had just taken place.
I'm sure this "sister" thinks she passes well, but my sympathy for her "polite" conversation went after the 2nd minute of probing questions with the poor girl. OK...she is still my "sister", but like Stephanie says, I don't happen to think she did herself, or the rest of us, any favours.
If we are honest, I think we all know times where we were a little over confident, and have walked around with "that sign" above our heads. If we keep our composure and go about our business without seeking attention, we will find we are mostly accepted with little more than a single glance or comment, and can learn from the experience.
Chrissty