Yes, we should keep them.
It's not a perfect solutions, but humans tend to be visual beings and keeping the flags will make your specific language forum easier to find by a first glance. Ditching them... How many of us have not ever read through a list several times in search of a name we knew was there but couldn't find?
read fluently, understand well, speak badly;
read fluently, understand badly, can't speak;
read some, understand a bit, speak a few sentences;
heritage language, want to understand and speak but can't.