Capping the SURNAME is a standard practice to determine direct lines. You can dream up many other widgets to use on Ancestry Member Trees, a little heart (your keyboard has symbols, hit "alt" to see them), a color field pic, the possibilities are endless.
Anything you put in the name field will affect the indexing. If you're concerned whether your data can be found by others searching for great grandpa John Smith, then don't put a symbol before the first letter of the surname.
You also want to consider that if you intend to download and export your ACOM Member Tree to upload to another site or desktop program, all those widgets probably aren't going to translate.
Figure out what's important and what visually works for you.
You might want to create a small test tree on Ancestry and tinker around with symbols, pics, etc. You can test how it will translate to other applications/programs/displays, and the indexing and searching.