"Mind the gap" offensive?

[BigT]

Copying over my guess (which apparently came just after you made this thread.)

@BigT

The only thing I can think of is that “gap” is also used to refer to a thigh gap. But that wouldn’t make much sense in context here, I wouldn’t think.

But I googled it, just to check. (I tried “mind the gap” obscene). And I found an old language forum post from 2009 where someone said

Last time I was in London I saw somewhere: “Mind the gap unless it’s between the legs of your girlfriend” or something like it.

So I guess maybe she’s only encountered it in that way? Or maybe she just assumed what the OP of that thread asked. Or, heck, maybe someone lied to her about what the phrase meant. ⁢