I was attempting to edit the top post of my Suggested Guide for Japanese Literacy and noticed now I cannot edit the first post and other older ones. I assume that you have the forum set-up to archive after 2 months.
Normally, this is not an issue. However course creators will likely be editing and adding information over time with regards to their course and they’ll want to do this to the top post as anything else will lost in all the comment replies. In addition, I link to the first post on other websites (mainly Reddit) and want it to have the most updated information.
Please consider removing the archive setting or at least don’t do it on Course Forum posts.
I don’t know the reasons for not allowing edits after a certain time. I’m thinking it’s probably to not to disturb the flow of conversation and to not let people edit or delete their posts after a time to do silly things.
That behavior is perhaps useful in certain kinds of forums and less so in other kinds of forums. I’m thinking here it’s not that useful as the majority of posts here are about the sharing of information (which can change) and not about discussion. So I think here the possible drawbacks of allowing edits do not outweigh the positives of it.
Here is another topic that ran into this problem:
Until Memrise gets around to changing it, you could ask here to have the post be made into a wiki: