We use Bitbucket Pull Requests Builder. Sometimes we need to start build again. So we use "test this please" comment on bitbucket pull request page. Build starts fine but after build is done it is started again. And again and again and it never stops until someone delete "test this please comment".

Step by step:

1) PR is created on bitbucket.
2) Jenkins run one build with success result
3) Someone add "test this please" comment on PR bitbucket page
4) Jenkins adds comment with some "hash" like on attachment
5) Jenkins run build with success result
6) Jenkins updates comment with some new hash value
and run again and again ..