I agree that it's important for people to be independent about locating and ingesting information. I also think that it's good to include a quick definition, particularly for stuff that's really specific (indeed - while looking for a definition I found a blog post that starts with "If you don't already know what Immediate Mode GUIs are then please stop now").
I did a Google search but there weren't any clear definitions on the first page or so.
I did search for the Wikipedia article and here's what I got:
"Immediate Mode GUI is a GUI where the event processing is directly controlled by the user. The key is the aspect of retained (RMGUI) vs non-retained UI (IMGUI). In the latter, the user code is holding on its own natural data, in the former it is stored in the GUI system, often hidden from the user code. The immediate mode GUI widget toolkits are more direct and thus less complex, thus they are a good choice for those who want a simple but easily changeable and extendable GUI toolkit, they are usually generic, open source and cross-platform. The original Immediate Mode GUI toolkit was imgui[1] which is based on OpenGL. The idea was popularized by Casey Muratori. There are others such as nuklear[2] with backends for several graphics libraries, kiss_sdl[3] for SDL (Simple DirectMedia Layer) or dear imgui[4] written in C++ (here the jvm port[5])."
First, the quality of this writing isn't great, to the point where it makes it harder to read.
I think that the above definition makes sense if you already know what Immediate Mode is, but it was pretty opaque on my first read (partly because I misunderstood "user" in the first sentence to mean "the customer sitting in front of the computer and using your IMGUI program", instead of "other code that uses the IMGUI").
The definition now makes sense to me after reading other posts here explaining that this was a Direct3D thing.
So yeah - I can see the arguments that we're not the target audience (and I understand that the person who posted this to HN probably isn't the author), but I think that Stratoscope's point that articles posted to the general HN audience would benefit from short, clear definitions (or links to definitions) in the articles is spot-on.
Also, props to Stratoscope for their calm, constructive replies in the face of a lot of disagreement! If we all did this (and I include myself here for sure) the Internet would be a better place.