To my mind, "don't be ridiculous" is not less rude than "what are you smoking?"
The first comment seems to be meant seriously and explicitly takes as a starting point that an interlocutor is "ridiculous", i.e., should be ridiculed/mocked for their comically stupid comment.
"What are you smoking?" is pretty clearly meant humourously and/or as an excuse to post a cat gif, so gets a pass from me on that basis.
To address the point, if the pipe from 1 to 3 is full of standing water, the pressure from below is zero (the lip of glass 3 is at the same level as the pipe end, give or take). The pressure from above is not negligible (due to the weight of the pipe up to three). If the water flows anywhere is will flow down the pipe, not up.
The whole thing is very silly though. There is no way to come up with any kind of answer without making all kinds of assumptions about what the diagram represents.
For example, one poster suggested the water would overflow glass 3 and pool on top of the pipes until it ran into glasses 6 and 7. That's only going to happen if these are some weird big flat pipes. If we assume the pipes are cylindrical then any water which lands on top of them will run to the underside locally and drip off, missing the glasses.
If we don't assume the pipes and glasses are cylindrical the all bets are off. What if they have no walls at all outside the plane of the diagram? Then nothing will ever fill up at all! What if there's a pipe we can't see from the bottom of glass 1 on the side facing us, linking it to the top of glass 7? Then 7 fills first. And so on....