When I topic is new I can edit it but if it’s old I’m no longer allowed to. Why? Is it a lock by this forum platform? Or can you change that by a setting?
For example, I can’t edit an old plugin post. Maybe the plugin name has changed or the instructions. The only two possibilities is then to add a reply or create a new topic.
If topics are too old, they cannot be changed by the original authors anymore. I don’t think we can do anything about that.
Too bad… except turn them into wikiposts manually, but that’s probably not ideal.
Even then you probably can’t change the title anymore. However we mods still can. 
So if you ask nicely …
I am allowed to change title and type, but not the text, for some reason.
Maybe that’s because editing posts months later may lead to people changing their whole discussions. I agree that this “feature” isn’t that useful for plugin topics though. 
Yes, mean people can put replies out of context, like this:
A mean guy: I released this plugin. What do you think?
A fan: It’s awesome!
After the edit:
A mean guy: Donald Trump will make America great again! Just grab them by the pu**y.
A fan: It’s awesome!
So I see the reason. 
Excellent example 
