Reddit isn't meant to be a source nor is Wikipedia, but it's a place to find information. They can be seen as central hubs to get information.
If a person comments on Reddit with a valid point and sources all his facts, why does it matter where said comment is made, and honestly, it doesn't matter if admins can edit it or not, really.
Look at it like posting an EXE and also linking to a credible site containing it's checksum. As long as you trust the linked site, then it doesn't matter where the EXE is posted and if someone has access to modifiying the EXE, all that matters is that 1. you got the data, 2. the data checksum matches the source.