I used to work in, and still follow as a hobby, a sport that is male dominated, although female participation is improving and I’m far from the only female fan. I’m a member of a few FB groups related to the sport and, in part because I used to work in the industry, I can post with some authority (e.g. answering questions about how certain aspects work) and because I’ve been a lifelong enthusiast I can remember esoteric facts or reminisce about less well known characters from back in the day when I contribute to discussions.
Invariably – and I do mean invariably – regardless of which group it is, at some point I end up receiving notifications that some random Joe Bloggs or other, always male, has messaged me. It’s usually after a post where I’ve made a contribution of the type referred to above, and there’s almost always a patronising ‘fancy you knowing that’ vibe to the messages (for clarity, the messages are from different men). I’ve got wise to this now and just ignore the messages and block anyone persistent or demanding but the first couple of times it happened I naively replied; one guy ended up practically spamming me on a daily basis with links to articles about the sport, including articles I’d commented on in the group that he’d clearly seen because he’d already liked or replied to my comment (as he did to every single one of my comments until I blocked him), and another tried to steer the conversation into a pick up situation, wanting to make plans to meet up at a sporting event. I should add that even when I used a profile photo that was of my face – I don’t now – I’m no vision of beauty so this is not a stealth boast of ‘how attractive am I?’ In fact it’s precisely because I didn’t/don’t expect men to find me attractive that I replied to the first two or three messages in all innocence in the first place.
I have a few male friends and ex-colleagues who follow the same sport and are members of the same or similar groups and I’ve asked them if they experience this. Quelle surprise, they don’t 
It happened again this morning: I’d posted advising someone about the history of a particular historical reference book for the sport – it’s one that has attained something of a mythic status amongst fans and only pops up on eBay etc in a certain format once in a blue moon, and the organisation I used to work for originally printed it back in the 1970s so I know its story – and lo and behold, a short while later up pops ‘James’ with a ‘ooh, what a clever girl you are to know that, what else do you know?’ type message. I actually have a sentence on my FB profile in the bio section that states I don’t respond to unsolicited messages even if we’re members of the same groups so the minute you click on my profile to send a message it’s RIGHT THERE that you’re crossing a boundary I have put in place. And yet…
I know I’m far from unique in experiencing this (which itself is a pretty damning indictment on entitled male behaviour) but it’s so irritatingly predictable, and I’m annoyed that at times I feel put off from chatting about a sport I love in case it encourages more of this behaviour. It’s the patronising, faux (or maybe not?) surprise that a woman could have an in-depth knowledge of the history and workings of the sport that particularly infuriates. It’s not quite mansplaining but it’s first cousin to it. Anyway, I’m sick of it and I wish it would stop.
Longer than anticipated rant over, thank you if you read this.