So if anyone suspects they are being ignored, they could change their avatar every day and mess with those who are ignoring them.

I was just going to say that.

It was intended to solve the problem I set out to solve.
With it displayed like this, you see its imperfections, but remember, this is how all software is developed.
This is perhaps the smallest type of program with the simplest goal, but the over all design process is not that different from projects with millions of lines of code.
The problem with computers is that they do exactly what they are told. Development time is also a problem. While a program's function may be easy to envision, actually writing that program and testing it can take a very long time.
So we have an incentive to do what works, no matter how inelegent. Also, some problems cannot be solved perfectly in a practical way.
This article may be of interest:
http://en.wikipedia.org/wiki/Worse_is_betterThe end of the article brings up "The Mythical Man-Month" (a good book). The design of good software often starts with a simple script which grows as it is needed until the final product is a lot more. This little script, if it were interesting to others, could perhaps be taken to new levels with incremental improvements and with perhaps someone starting it over with a larger goal.
That being said, it does work for the users requirements. The user was me, and it does exactly what I want it to do.
Realistically, people usually retain an avatar for a while. Just like someone can always circumvent a ban, someone could easily negate this script, but both actions are sort of "anti-forum". A person who changes his avatar very frequently just annoys more people than the person who happens to block his posts.
However, there is a way to be more robust. I could have developed it to go by user id, however, that would be more work.
The user id is what I'd want because that is the only thing which would be unique. I would have had to have found a way to get "998657" from a link in a certain position in the forum structure without it adversely affecting other parts of the forum. It is possible, but it is much more complex.
The method my program uses is very short and it has no side effects. The method I give above has several side effects. One of them that this sort of link is also found on places other than the the individuals posts and the simple way of blocking the post I use would result in large parts of the site being blocked if it were that greedy.
On the other hand, explaining this problem resulted in me finding a more simple solution to that sort of approach...the "send a person message" link we all have under our names is not found anywhere else on the forum displays, so if I used that, I could probably reuse the same code with no side effects, but just using a different element to latch onto.
But there is no problem, so I am not going to fix it.