@aseriesofstillimages
I still disagree, though, that a lesbian cannot continue to consider herself a lesbian if she is attracted to and has sex with a trans woman who has a penis. I just don’t think everyone has to define their sexuality solely on the basis of genitals. A lesbian who found herself attracted to a trans woman with a penis might then consider herself to be bisexual, but I don’t think it’s for other people to tell her what she is. There are so many aspects to sexuality and attraction, it isn’t just about genitals, or even just about sex.
I think the "vegetarian" analogy is helpful here to explain in what contexts it's an issue, and in what contexts it's not an issue.
A vegetarian is someone who doesn't eat meat, including chicken or fish. For food to be labelled as vegetarian it must not include any substance which required the death of an animal to produce it - so no gelatine or meat stock as well as no actual meat. Some people who consider themselves vegetarians aren't that strict, don't worry about making sure that their cheese and wine and chocolate puddings are properly vegetarian. Some people do actually eat chicken and fish but prefer to describe themselves as vegetarian because they usually enjoy the vegetarian options at good restaurants that have nice veggie offerings. But they will occasionally choose to eat fish.
It's not actually a problem for them to describe themselves as vegetarian or think of themselves as vegetarian when it's only them who are affected, but if they don't acknowledge at all that their fish-eating isn't technically part of vegetarianism then it does actually do damage to vegetarianism generally because the wider population get mixed messages about what vegetarianism means. I did actually get given squid as the "vegetarian option" on a flight once, and on another occasion at a canteen on a (fairly isolated) science research station the veggie meal was mackerel. Imagine going to a new vegetarian restaurant, as a vegetarian that doesn't eat fish, very excited that there's a new veggie restaurant in town, and finding that it's actually a seafood restaurant and the only thing on the menu you can eat is the chips. That's exactly what it can be like on some trans-inclusive lesbian dating apps.
Now imagine you aren't allowed to say "but I am an actual non-fish-eating vegetarian" for fear that you will upset the fish-eating vegetarians or invalidate their identity.
So within this analogy, it is good practice for fish-eating vegetarians to be clear, in contexts where their choices might cause others to make incorrect assumptions about the choices of other vegetarians, that there is a difference. No one will stop them going into the vegetarian restaurant or from ordering the veggie option elsewhere if they fancy it, but when there's a family wedding being organised where the main course is beef and they hear that the "veggie option" is going to be salmon, they need to be saying "hang on, that works fine for me but we need to consider the actual vegetarians too"
Of course dating isn't just about genitals or just about sex - there are a great many really fulfilling platonic relationship couples for whom sex isn't a big deal and they are more attracted to each other's personalities and an ongoing life partnership and what goes on in bed isn't particularly a priority. And if that's the kind of relationship you want then that's great.
But it's become actually forbidden for a woman who wants a full-on vag&clit orgasmic sexual relationship with another woman to explictly say so, or even vaguely and discretely hint that this might be on the cards by specifying that someone being biologically the XX variety of human is part of what they are looking for in a partner. That is highly misogynistic and lesbophobic.
Women who like sex with women and who also like sex with men or who aren't that bothered about sex generally and are more in it for other parts of the relationship that aren't about the genitals, and who aren't too bothered if their new "girlfriend" doesn't have a clit, are very much free to live their best life and self-describe as they choose in contexts where their choice has no impact on others. So it does no harm for them to self-describe as a lesbian when joining a lesbian walking group or lesbian book club to meet other women. But it very much does do harm when they try to impose their own definitions on such clubs and groups and make them male-inclusive, they do need to understand that their own self-definition doesn't apply to everyone and therefore some lesbian-centred services and facilities are going to have a tighter definition than they personally need, and that's OK.