What basis do you have for concluding it was an anti-trans false-flag operation in this poster's case? Nothing in their post would lead me to naturally reach that conclusion. Downplaying or instantly dismissing this kind of anecdata as the result of a "false flag" is naive at best and dangerous at worst.

Speaking from my own experience, I've seen a lot of stuff on Tumblr that leads me to think there's a very active, very angry, very threatening trans lobby on the platform. I've seen repeated threats of violence and worse from trans-identified individuals directed at feminists who want maintain female-only safe-spaces. These posts are rarely taken down and the community will often rally against the "TERFs" being threatened ("Trans-Exclusionary Radical Feminists").

I know one woman who'd posted about keeping changing rooms for females separated on a sex basis. Her employer and college were contacted repeatedly by a pair of people who said she was spreading hate-speech online. Their goal seems to have been to have her fired. These same people had been making threats of violence against her, culminating in a rape threat. At this point the police became involved and I'm not sure how it's since been resolved.

Obviously this is a tiny minority of people but it's a tiny minority that often aren't actively censured or disowned by the larger community, and whose extreme views are reinforced by a sympathetic echo-chamber of like-minded people. Some may be "false-flags", but I don't think they're in the majority by any means.