Thanks, now I know what those are about. Learn something new every day. Even old goats can learn!
The pattern appears to be that a new account is created and then the spam posting starts by using the new account to post random numbers in successive posts into an existing thread. I suspect this is used to build up a posting history before starting new threads. I don't know if ARRSE enforces a rule like that, but many forums require that new members post a certain number of times in existing threads before they are allowed to start a new one of their own and the spammers will be following an SOP.
With the posting history established the spam account will then start new threads with text in Chinese characters and the name of a western English language university. I noticed that Canadian and Australian universities are frequently mentioned.
The intention is likely to try to make the spammer's web site rank more highly in Google by creating numerous references to it in long established web sites. Search engines typically rank a web site more highly if there are references to it in other "reputable" web sites, where being long established and constantly active count towards giving a good reputation.
The ultimate goal is to direct more traffic to the spammer's own web site by making it rank higher in search engines. Presumably they are making money by displaying ads on web pages to Chinese students who are trying to find information about foreign universities that they would like to attend.
The spammers are undoubtedly spamming large numbers of forums with identical posts shotgun style. The mods will clear them out, but they only need to stay long enough for Google (and other search engines) to notice them and give them a "bump" upwards in search rankings. It's all a numbers game. The spammers themselves might not be the owners of the web site they are promoting, they might be getting paid for their work, possibly by getting a cut of the ad revenue.
I suspect the spamming is all automated using scripts. It is possible though that the account sign-up might be manual as the user names seem to be quite heavy on the use of "q" and "w". That however might just be an artefact of whatever algorithm they are using to create new user names. ARRSE uses "Xenforo" forum software. The spammers are likely targeting loads of other forums which also use the same software so they can use the same spam scripts on all of them.
For amusement the other night I wrote a proof of concept script which would "scrape" the "new posts" web page and detect when a new spam "run" had started by looking for an excessive number of non-English characters in the title and summary. It seemed to work pretty well, although it just tells you the spammers have started and doesn't on its own do anything to stop them. The spammers are pretty predictable though, which is (among other reasons) why I think they are using scripts.