You should always report a bug on Tibia and NEVER abuse a game bug. However, you should do this because it is right, since there is no reward or any kind of benefit after reporting an important bug on most of the ordinary occasions. There is no system that will guarantee anything for your effort, but rest assured that we had several cases in the past were we could see special prize items given to players that contributed for bug corrections on test servers. The Famous Golden Bug, for example https://www.tibiawiki.com.br/wiki/The_Famous_Golden_Bug
It is theorized that legendary items were inserted on Tibia back in the days through bug reports that were rewarded. People question the origin of these items, as some people claim that we also had now quests that aren't anymore active on Tibia, but it is fair to say that if Tibia had a policy to reward more often bug reports in the past, this tendency became now more attached to really game breaking bugs. Like I mentioned above, on 2012, Val'Mukka received the item "some golden fruits" after denouncing an important bug related to the mentioned item https://forums.tibiabr.com/threads/448124-Jogador-recompensado-ao-reportar-bug%21
I received the following message on a Ticket after reporting not one, but two bugs with appropriate images attached showing the bug encountered while playing the game on a regular server. This was the answer that I received when I questioned if there are rewards for bug reports:
Hello CENSORED,
Thank you for your request. I understand that you'd like to get a reward for letting us know about this issue.
Of course we are grateful for your bug report. Please understand that we usually don't hand out rewards. Reporting bugs is something players do for the benefit of the whole community.
Let me know if I can help you with anything else.
Kind regards,
Bolkar
CipSoft Tech Support
Keep in mind that this is an official confirmation made by a Cipsoft employee. Thus, we can understand that the occasions where bug reports are "thanked" by Cipsoft with a bonus item aren't the rule to be followed and they aren't guaranteed at all.