On our internal dogfood work item system I have had an interesting experience these last few days. A custom work item type we have has grown into a situation where we are sticking aggregated information into the comment string field of the links tab instead of individual queryable atomic data fields in the work item. That makes it hard to query, and there is now a lot of data stuck in a text field very hard to query on and that I have to maintain manually.
In my gut this is all eerily familiar.
It all boils down to Databases 101. IANADBA (I am not a DBA) but during database design it's typically recommended to split out all the data fields into the most atomic queryable units possible. Same advice applies to custom work item type creation in my opinion.
So anyway, my suggestion - save yourself the trouble and don't put information you'll want to query on inside this comment field area: