I'd say it's a bit too aggressive but your honesty is very welcome as a non-deliberate act a la certain large companies. And to repeat, I do like my Leikr! You can get a similar non-destructive effect by defaulting to only showing the last six months posts rather than all topics in a forum (except for the software release forum).
Two pinned topics with a list of feature requests and bugs including those resolved would cover most users repeated requests and queries (and wouldn't be something on your website anyway). Something similar to the Kobo firmware bug thread . Unfortunately, this forum isn't set to allow editing of posts (not a purged ) otherwise I'd maintain it myself - as to be useful you need to keep it updated in the topics first post.
Post editing is definitely supported in your phpBB 3.011 version and there are also a variety of anti-spam measures you can use too given the latest spam attack.