Without context of the use case or what you are trying to achieve, the short answer is yes (as can be seen below):
I entered the following text successfully: [ ]
What information would you like to capture between the brackets?
Thanks for the reply!
My questions are:
1. Can the brackets be used in Promapp?
2. And, if so are the brackets being used correctly?
3. And any other tips regarding bracket usage that would be good to know?
As shown above it is possible, however I'm not sure why you'd want to start a task or activity with brackets. I'm guessing the example you gave is from imported (or exported) text, which requires specific formatting to ensure Promapp interprets it and shows it properly when imported.
If you're adopting Nintex's best practice writing principles, all activities and tasks will start with a verb, thereby meaning you would not start any activity or task with brackets.
You could use brackets within the text of either an activity or task, and it will depend on the content as to whether that's appropriate e.g. it might be more appropriate to include the backeted text as a note.
I agree, that's how I expect it as well!
I now know you can use them however, probably not the best practice!
And I also understand that the they may have been imported.
I really appreciate all responses.