Since a recent poster has stated that they did not read the rule about posting for research purposes, perhaps an explicit question, requiring a yes or no answer could be included in the sign up process, for example "will you post details of research with the aim of gaining participants?" If the applicant indicates "no", then the sign up application continues. If the applicant indicates "yes" they could be directed or automatically forwarded to the relevant information on the website which relates to seeking permission and approval before using the forum. This could be coupled with moderators receiving a note of the chosen username, so they can actively check New posts, in case the person changes their mind, indicates "no" and proceeds regardless. Furthermore, a function linked to the chosen username could detect whether the sequence of letters "student" or "research" is included and a prompt about the relevant rule.
Ok, so the rules are openly available for all. People signing up should read rules when joining. But it is apparent that this is not always happening, or at least from time to time people posting unapproved unpermitted research requests are saying they have not read the rule(s). So these additional measures would hopefully cut down on this problem.