On the subject of posting there are four questions: do you ever post? Do you never post? Do you sometimes post? If so, when do you choose to post or not?
I never post. I used to but I found it unwieldy with bigger pens. I gradually gave it up with smaller pens, too. If there is nowhere secure to set the cap I hold it in my other hand.
There are people with expensive new pens who do not post because it will mark the barrel. This is correct; it assuredly will. Part of the reason I don’t post is similar. Most of my own pens are vintage and several models are subject to cracking of the thin cap lip, which can arise from posting too forcefully. That isn’t the main reason for cap lip damage but it’s worth avoiding.
Another reason is balance. I have never written with a posted full-size Duofold, as an example, because it would be uncomfortably back heavy. Through time, I suppose I developed some form of muscle memory about pen balance and now I wouldn’t be comfortable posting even a small pen like a Swan 3160.
There are a few pens I am aware of that were designed to be posted. 1920s and 1930s cheap hard rubber pens were often threaded on the back of the barrel to accept the cap. Conway Stewart’s cheapest pen of the era also had threading on the back of the barrel. I believe it was a pen intended to be bought cheaply in quantity by employers, a forerunner of the Crystal Bic. If I had one I wouldn’t post those pens either. There may be other pens configured in this way of which I am unaware.
For years I have seen discussions on this subject with people posting opposing reasons for posting or not posting. They seem to me to be good reasons but neither are decisive. There’s no real deal-breaker in the world of posting. If you like to post, you post; if you don’t, you don’t. Or maybe you just say the hell with it all and buy a Pilot Capless.