Luis This sounds like your comments field is set to “Record multiple Responses”. If you go in to Admin, Prospect Fields, Default Fields, and try editing that field to turn off a tickbox for that option. It’s may not be available to turn on/off.

I have used the API to reformat the comments field as it can be hard to read. I used a REGEX to look for the time stamp, and added more space around this so it looked like a header. I also added extra line breaks around paragraphs and such. SFDC honors this formatting much better than Pardot does, but the people needing to read the comments and action them are doing so in SFDC so this works out.
I would also pull in other interesting fields from Pardot but didn’t rate a SFDC Synced field. This is really good for tradeshows because they can give you dozens of really interesting fields that don’t map to your Pardot & Salesforce, so I put them into the comments in a way that is actually readable.

If you click into the template and scroll down the page, there’s a “usage” box that tells you if it’s in use by Engagement Studio or other automated workflows.

If you try to delete something that’s in use, Pardot actually won’t let you… so I usually just flag the ones I *think* are old, try to delete, and let Pardot save me from myself if I’m wrong 🙂