What is it with some people..

then you should've said jack base. but my point is still relevant, pointing that out serves no purpose in the thread. it'd be along the same lines of: hey, i see you have old tires, i have some i just took off are you interested? what purpose does that serve?

and yes, i would consider it improper to interrupt a conversation that was already in progress to ask a stranger if they wanted a jack base. because that's what a thread is, it's a conversation.

so again, tell us all how that this is a limitation? is it the persecution that you can't freely insert yourself into the conversation with a non sequitur, thus junking up a thread? is it the annoyance of having to send a DM? is it because you want to do so publicly so that there is an appearance of being a "good guy"?

i guess the question eventually becomes: why does it concern you so much?
If a conversation were already in progress about the person's car it would not be an interuption to point out that you have a jack base if you notice they are missing one. If we can't agree on that this conversation is useless.
I wouldn't think twice about asking a person if they would be interested in something I saw missing while they were showing their car. I think that could be helpful and probably be appreciated, especially if they were looking for one, even if they didn't bring up the fact they needed one. I can't see where you are coming from . This is not irrational behavior when out talking about cars.

It may be considered irrational and/or at least improper here, by you and some others and it is what it is.