@J-Brouwer
why cannot one edit an own topic anymore after 5 minutes
Until very recently, it was a 3 minute limit! :-)
The reason for it is more complicated, but I like to think of it as not allowing history to be changed, because it can make other history not make sense.
If someone says something in a post, and 5 replies happen to a specific point in that original post because the user made a typo, fixing the typo 5 posts ago invalidates the logic of the additional posts. (Typos are one thing, other “mistakes” are more important – but maybe you get the idea)
If you post something, and later find you have additional information or realize you made a mistake, simply add an another post with clarifying data.
There was investigation into the possibility of letting the current final poster in a thread edit it with no time limit, but apparently the forum software – BTW, not affiliated with Notepad++ in any way; it is just software used, much like you use Notepad++ but don’t have control over its code – doesn’t offer that as a feature.