I.H.S religious tombstone inscription

ifconfig

One of the tombstone inscriptions which is attributed to having been erected by a relative of ours in the 19th or 18th century uses the monogram :

"IHS"
http://www.newadvent.org/cathen/07649a.htm

Having grown up myself in the RC faith I am familiar with this.
However, I'm just wondering if this was more or less used exclusively by members of the RC religion.
I ask this because we are aware that our ancestors were, for some time in the early 18th century, Church of Ireland protestants.
My suspicion is that this inscription relates to the period of time after they had converted.

On a broader note is there anyone here who has, via their family history studies found instances of their family having converted from Protestant to RC in the mid-to-late 18th century (particularly 1770-1790) ?
I realise that Ne Temere was a factor which contributed to conversions in that direction from the very early 20th century.
I also have read about there having been some "slight" relaxation of penal laws in the latter part of the 18th century.

The context in which our relatives found themselves we suspect was as Protestants without a very large support network (or the same level of security as the more well heeled landed classes). It may well have been that nominally changing their religious affiliation may have made their relationships with the peers with which they met and worked with on a daily basis a good deal better.

-ifc