I want to reply to a poster on such thread legitimately

That should be all you need to consider. A node is just a node and if you think that the reply would be a net benefit to the monastery then post it. I suppose that it's conceivable that the reply might only be of benefit to the parent author in which case you could msg them instead but such cases are probably few and far between.

I have been accused of raising posts for XP+ before, but those who raised that are irrelevant to me.

Quite right - water off a duck's back. Life's too short.

Out of the many ways to get XP (coming everyday, using all your votes...), posting actual content has to be the least undeserving one. Your input might actually help someone or help you by letting another monk improve your answer, or correct it. So go for it, the fact that you do gain XP (probably) shows that some people did think that your answer was worth posting.

There may be a "don't feed the troll" clause in there though. Mainly I'm thinking about this thread , which I was kind of disappointed to see come back from the dead, because of all the heat in the discussion, and the fact that it wasn't that useful because mostly centered around one person. I just decided not to upvote posts in that thread even if I agreed with them (easily done since I basically ignored the whole thread), so it's not like I have a strong opinion against posting even in that case. I just think threads heavily featured in worst node don't need more publicity.

tl;dr: Quality first, everything else subordinate.

Have a look at Nostradamus Five Year Node Reputation Prophecy Expires Today!. AFAICT, its sole purpose was to take the mickey out of a true believer. There was no technical content and the node that started the discussion was substantially upvoted. And yet there were "no significant downvotes" anywhere in the thread. So it seems to me that dozens of monks, at least, respond by having a good giggle. And so we should.

There is a strong bias here against changing history, on the basis that questions and answers should be available so people can avoid repeating questions. Sometimes a question or explanation isn't clear, or a better solution becomes available over time. I'm all in favour of this site containing the best information that we can provide, so when, for example, HelenCr asked about my answer to Inserting copied rows at another position in Excel nearly two years later, I had no issue about clarifying my points, not just for her but for anyone else. I suspect that I have upvoted more posts "of a certain age" than current posts, because so many of my questions have been well answered without the need for me to ask them.

Regards,

John Davies

I have been accused of raising posts for XP+ before

If your answer is legitimate, go ahead, post it! Perhaps not too many people will see it immediately (at least not those monks -like me- looking mostly at new threads), but it will presumably be useful for future readers coming across that thread from a search engine.

but I don't want it realized that I'm doing it in order to get exposure on the overall hierarchical post

Nobody knows why you are doing whatever unless you explicitly state that. People guess, lottery, raffle 'tis called.

Just ignore timestamps. This whole PerlMonks database has been created, and will perish, in a blink of an eye, compared to nuclear waste persistence in terms of a humans lifetime.