The one by coder777 doesn't seem like spam, but the first and last links do.
coder777's 220803 links filesuffix.com, which has googleadservice ads on the borders, but it isn't spam in itself.
, the first sentence is copy-pasted from some help blog that isn't advertising a product, but then the second sentence attaches on a bad grammar "Here is link to fix [Fill in the blank] error".
link to possible spam sites. A GitHub page by username kevin-brown lists both of the sites linked as spam sites: https://gist.github.com/kevin-brown/3f22cd3cda906a60012a
I don't know the authority kevin-brown has on listing what counts as a spam site, but he's probably correct.
It's interesting spam, it seems to search keywords from the post on google, and copy related sentences, but then insert their own spam website as if that's the solution to their problem. Reminds me of https://xkcd.com/810/
, but still malicious in this case.
Anyway, I say remove link/user 1 and link/user 3 for spam, but not the OPs: I think it's reasonable to say the OPs are posing valid questions, they could have made the account to post the question. I don't think asking "what is this file extension" is malicious even if it is easily web-searchable.