What has happened?
If we focus on the end of the gene, the isolate sequence appears to be "sticking out" in comparison to the other alleles (the sequences we downloaded from PubMLST). If you look carefully, you can see this is due to the addition of an "A" base shown by the arrow.
This has led to a frameshift. So the original stop codon is now out of frame.
What does this mean for a bacterium?
In a bacterium, the protein machinery would continue until it reaches the stop codon identified by Zooniverse users. This would mean a longer protein is made. This could be possible if the extra amino acids don't affect how the protein folds. In vivo studies would need to be run to test this.
What would a curator do?
A curator would create a new allele that goes up to the identified stop codon.