The telegram bot is registered text based, which you need to input your username for you to get notified when someone mention you or quote your post, actually you can register other usernames too. If the registered btt username in telegram is your old btt username and it was mentioned or quoted by someone then possibly you will still receive a notification. Until you changed it, or use the track phrase with your old or new username instead.
True but that's only if members were to mention their old user names and for what reasons? And when users changes names on the forum, just few members would recognize their old names( those are members who were on the forum before the changes were made). I have tried searching before for old user names using ninjastic.space but it's not possible. Let's wait though for the above mentioned to reply and share their experience.
There’s a feature on the notifier bot that allows you to track a phrase or track user(I’m not sure if this will work) so that you will be notified incase someone mention that exact phrase on this case their old username. These user that change username probably track their old username for the mention in case someone still doesn’t know their new username.
As @PX-Z said, Telegram bot will just notify you based on what you set during the startup.
@Tryninja sir, I still didn’t try if the bot will work if you input different UID to a username. Will the bot gives you a notification from 2 accounts?