Free will doesn't come into it.
There are only two alternatives:
1. Your action changes the world
2. Your action doesn't change the world
In relation to your posting or not posting:
(a) yes it's perfectly plausible that your post causes a snowball or cascade of changes, leading to a radically different world in 1 week or 1 year's time
but
(b) it's also perfectly plausible to generate an identical scenario (to one in which you didn't post) in 1 week or 1 year's time, because nobody remembers or cares by then, and the time that was spent posting and replying would otherwise have been wasted on posting and replying to other posts.
Now you might argue that there are 1 billion or 1 trillion or 1 googol ways (i.e. timelines) for (a) to happen, but only 1 or a few ways (i.e. timelines) for (b) to happen --- but even if we were all to accept that -- it doesn't mean that (b) couldn't happen -- and since we choose which timelines to discuss, we might choose to focus on (b) scenarios because we find them interesting.
Want an example, we all know (the exact numbers don't matter, but the principle does):
Let's say it's the American Revolution as the PoD. The loyalist lose. There are various alternate ways that could happen. In 99.9% of cases they go to Canada, return home, etc. that still leaves 0.1% of cases for them to go South Africa
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases it leads to a pretty typical colony in South Africa, but in 0.1% leads to a Antipodean Prussia slave state called Drakia/Draka
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases, the world is gradually more and more unrecognizable, but in 0.1% of cases, it leads to a world with Nazis, Soviets, etc., as well as Draka
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases, the Draka are crushed, or the world is destroyed by nuclear war, but in 0.1% of cases the Draka have conquered the world by 2009.
Now go back. Let's say there's 1,000,000,000,000 possible timelines
Let's say it's the American Revolution as the PoD. The loyalist loose. There are various alternate ways that could happen. In 99.9% of cases they go to Canada, return home, etc. that still leaves 0.1% of cases for them to go South Africa --- so that gives 1,000,000,000 timelines with Loyalists in South Africa (and 999,000,000,000 without them)
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases it leads to a pretty typical colony in South Africa, but in 0.1% leads to a Antipodean Prussia slave state called Drakia/Draka -- so that gives 1,000,000 timelines with the proto-Draka appearing (and 999,999,000,000 without them appearing or them not being proto-Draka)
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases, the world is gradually more and more unrecognizable, but in 0.1% of cases, it leads to a world with Nazis, Soviets, etc., as well as Draka -- so that gives 1,000 timelines with Draka + Nazis + Soviets (and 999,999,999,000 without Draka + Nazis + Soviets)
Out of those cases (the 0.1% from previous paragraph), in 99.9% cases, the Draka are crushed, or the world is destroyed by nuclear war, but in 0.1% of cases the Draka have conquered the world by 2009. -- so that gives 1 timeline where the Draka conquers the world (and 999,999,999,999 where the Draka don't exist, or don't succeed if they do)
As far as I am concerned, it doesn't matter that there are vastly more possibilities without Draka or without Draka + Nazis + Soviets -- just because I'm interested, I see nothing wrong with discussing any of them - even if it's only one of the 1,000 or 1 timeline with Draka world conquest.
Remember also that all the timelines aee equally plausible and valid -- we are not considerably impossible timelines (what if magic became real and there were superheroes!) -- yes, non-Draka timelines may be more common, but any individual Draka or non-Draka timeline is just as likely as any other individual Draka or non-Draka timeline.